Lassen and Great Basin National Parks with a stop in between for Lake Tahoe.

OK, From Great Basin NP, take US Rt 50 to Carson City, NV. This is "America's Loneliest Highway". You'll go through Ely and a few other small towns. At Carson City, head south a bit to the small town of Genoa, NV. Stop in at the Genoa Bar and Saloon, Nevada's oldest continuously operated saloon. A little south of there, hang a right onto Kingsbury Grade Rd and it is over the mountain to the vista of Lake Tahoe.

Speaking of historic pubs, before you get to Carson City, you might want to peel off to Virginia City and visit the Bucket of Blood Saloon. Live music often.

Unless you time your trip for after Labor Day you'll be dealing with the crowds in the Lake Tahoe region - it's beautiful but has become a victim of its own popularity, so be prepared for that.
An interesting side trip is the town of Truckee just west of the Lake. There's a state park there dedicated to the Donner Party of 1846, and Donner Pass itself is just a little further to the west. Both sites are much less visited than the area around Tahoe, in fact you might consider staying in the vicinity of Donner Lake and just doing Lake Tahoe as a day trip, which will probably be enough to satisfy your curiosity. As I recall there are some scenic hikes in the vicinity of Donner Pass too, so if that's your thing you might enjoy staying a few days in the area. Note that some of the hikes get well up into the mountains (ie 8,000 - 10,000 ft) so you might need to take it easy until you acclimate to the altitude.
In Great Basin you'll be visiting one of the unappreciated little gems of the NP system. Though we didn't camp there, the campgrounds we passed on our hikes looked pretty nice. There too you'll be dealing with the altitude with the most popular trails - the Bristlecone and Glacier trails - topping out at about 10,000 ft., so there'll be a bit of huffing and puffing involved. Worth it though - the scenic vistas are spectacular. Probably worth a couple of days. Though the park itself is terrific, note that the drive getting there is through a true moonscape - flat and featureless (and bloody hot) until you get to the vicinity of the park.

Good choices. We drive right by Great Basin when we go from our summer timeshare in the Wasatch (Snowbird, Utah) to Yosemite and keep saying we need to stop and explore, but have not yet done that, the suggestion to take Highway 50 is excellent; it is a beautiful drive.

Lassen is a beautiful park with lots of hiking on offer. The main campgrounds may be fully booked, but there are more remote ones, such as Butte Lake, which may work for you. Or a California state park nearby, Burney Falls. We camped there last summer with our tent, after the Butte Lake campsite became unworkable due to lack of water.

Map of campsites around Lassen:

http://www.parkcamper.com/LV/Lassen-Volcanic-National-Park-Camping.htm

As for Lake Tahoe, my favorite Campground is at Fallen Leaf Lake, near South Tahoe and right on the lake of this name. It is a gateway to hikes in the Desolation Valley Wilderness. But this Campground is popular and reservations fill up quickly. Sugar Pine Point (a California state park) right on Lake Tahoe just south of Tahoe City is also very popular and fills up the day reservations are released. Or there is a private Campground at Camp Richardson, just north of South Lake Tahoe near the Fallen Leaf Lake road junction.

There are some forest service campgrounds nearby (not right on Lake Tahoe) which are much more easily reserved. Last summer we camped at Goose Meadow, on the road between Truckee and Tahoe City, right on the Truckee River near the entrance to Squaw Valley ( aka Olympic Valley). This was mid-July and the only others in the camp were two families from Germany camping in rented RV's. We had a nice evening talking to them and sharing a few bottles of wine. There are other forest service campgrounds along this road if that one is full. Here is a map:

http://www.arounddonnersummit.com/lodging/truckee_river_camping.html

Donner Lake is nice for swimming (warmer than Lake Tahoe) and you can hike on the Pacific Crest Trail from Donner Summit. There may be SUP and kayak rentals on the lake, as I saw lots of people doing that, but I do not know the specifics.

I think the best hiking around is in Desolation Wilderness, accessible from the Glen Alpine trailhead at Fallen Leaf, or a few other places nearby.

Great information, thank you. Unfortunately we travel at the beginning of August before our daughters go back to college. Contacting Lassen (finally) I was able to find out that the reserve able campsites are indeed pretty much booked, but we should be able to get a nonreserveable site or at worst camp 5 miles from the park in a National Forest. I need to research Great Basin some more but it seems campsites are not an issue. We would be "hitting" the Lake Tahoe area midweek week, so I'm hoping we'll find something there. I appreciate the information on Nevada drives. I'm a little confused probably more by Fodor's guidebook than by the information here. If I'm understanding correctly, the "loneliest" highway is highway 50 from the park west to Ely. Fodor talks about a U.S. 93 scenic byway "68 miles between the park and Ely", which looks to be highway 50 and NOT 93. But then I see a highway 93 coming out of Vegas. We are hoping that the campsites we end up are at some altitude, because Great Basin and Lassen do seem like they get quite hot. We call our tent the "inferno" when the days have been hot. ;)

@Lola, have you done the hike up to Lassen Peak? Looks like 5 miles round trip with 2000 ft elevation change. We are pretty sure we did a similar hike in Washington at North Cascades and no one died. ;) It sounds like a spectacular hike

Lassen Peak trail is an enjoyable walk to the top. The must do Lassen walk is the Bumpus Hell trail.

Edgar, thanks, we'll do Bumpus. Are you saying to Lassen Peak is easy? Oh, and I live at an elevation of about 700ft.

Some random thoughts and observations ...

The Bumpass Hell trail in Lassen is closed this year.

I grew up camping at Burney Falls and agree it's a great place if Lassen is full, or even if it isn't. You should try to make reservations if you want to camp there.

If you like trains, stop at the Western Pacific Railroad Museum in Portola on your way from Tahoe to Lassen. There's an entire yard of full-size engines and cars that you can climb on and look inside, and you can even arrange to drive the engines back and forth if you like.

If Lassen is too crowded or you run out of things to do there, look into visiting Lava Beds National Monument and/or Mt Shasta, which are not too far up the road. The views of Shasta from I-5 are really impressive.

Too bad about the Bumpus Hell Trail closure. Bad timing in that it looks like the closure is for this season. Alternatives: https://www.nps.gov/lavo/planyourvisit/exploring-the-hydrothermal-areas.htm

Lassen Peak is a hike but not technical. Sturdy hiking shoes/boots are a good idea but the walk is on a maintained trail. The trailhead does start at about 8500 ft asl. If you are more of a sea level person, the walk may become a step then a breath walking pace. But its not a scramble. Bring water, sunscreen and the usual hiking gear (hat, sunglasses, windbreaker etc) and a picnic lunch to enjoy along with the views.

The Rubicon Trail in Lake Tahoe is gorgeous. I believe we accessed it close to D.L. Bliss Park. I would have hiked something more strenuous but I was with my parents (they're in their early 70s and in good shape, but not as spry as a 40 some year old who hikes all the time).

https://www.theoutbound.com/lake-tahoe/hiking/hike-the-rubicon-trail

I found the TI offices in Lake Tahoe to be very helpful in providing info I didn't get from guidebooks, especially decent trail maps. Once you're on the ground, I would recommend visiting one of them if you want a more local and detailed perspective.

Thanks so much for all the great comments. I've read and researched the ideas quite carefully. So it looks like my best bet for camping in the Lake Tahoe area, would be a National Forest Campground, at least the ones I've looked at have non reserveable sites. Wondering if those of you with experience/knowledge of the area would have suggestions for particular campgrounds or areas to concentrate our search. My guess is that we are going to have to "wing it" after we leave Lassen. We do have the benefit of being in the Tahoe area beginning/mid week. Since we've never been in that area, I think we want to concentrate our time on the area quite close to Lake Tahoe. I'm also noting there is a road around Lake Tahoe. Are there particular segments that are more picturesque than others? I'm not asking for someone to do research for me, but if you already have ideas/thoughts it would save me some "surfing". Our interests are more along the lines of hiking/photography and we enjoy mountain and lake vistas. Probably less swimming and no boating. Our plan is to go to Lassen, then Lake Tahoe then Great Basin. Thanks

P.S. We love craft breweries where we can enjoy beers and bring in our own food. This is especially nice in the case of rain/heat where we are trying to escape the elements. Any suggestions for the areas I'll be traveling?

...craft breweries....

After leaving Lassen NP and heading towwards Lake Tahoe/Truckee swing through Chico. While Sierra Nevada is far from a micro brewery, Sierra Nevada is a early craft brewery that still puts out good brews. A good place for lunch and a brew if you are over 21:
https://sierranevada.com/brewery/california/brewery-tour
If you want to do the tour, reservations are suggested.

How much time do you have for Lake Tahoe? The road that circles the entire lake is about 70 miles but it takes much longer than it would seem to complete it - the reason is there is tons of traffic in the summer at certain chokepoints (and Lake Tahoe is quite developed in places like South Lake Tahoe, etc) and there are so many busy overlooks and stop-off points. The road is very much worth driving, and there are even offshoots from the road in several directions that add extra time (I loved Truckee and Donner Pass but was underwhelmed by Squaw Valley Ski Resort, for example). I liked the western (CA) part of the circle better than the eastern (NV) part (we started in Stateline on the NV side) because there were truly stunning spots on the way that stand out more in my mind - Emerald Bay, D L Bliss State Park, etc.

It seems like you'd see a major portion of the road if you come from Lassen via Truckee (northwest of Lake Tahoe), go south along the western edge of the lake, continue counterclockwise and eventually pop out on Rte 50 on the eastern side on the way to the Great Basin. By the way, just Google "Truckee microbrews" - there is much more out there in the Truckee area than the very well-known Sierra Nevada. Truckee is worth a stop - neat places to eat/ drink and very pleasant.

Good, quick web resources on the Lake Tahoe road:
https://visitinglaketahoe.com/most-beautiful-drive/
https://visitinglaketahoe.com/wp-content/uploads/2018/03/Most-Beautiful-Drive-Brochure.pdf

You could spend a week in Lake Tahoe (like we did, on a 3rd or 4th trip there) and still not see everything you want. The summer traffic was a drag, for sure. I hope you have more than 2 full days at the least.