jeff & kim,
First of all, congratulations on your 30th anniversary! That's a wonderful milestone.
As previously mentioned, July & August are not the most ideal times for visiting the Cinque Terre, but that's also true for other parts of Italy. It's going to be hot and crowded wherever you decide to go. It will be essential to reserve accommodations well in advance, and that's especially true for the Cinque Terre. If you can get a booking, try Hotel Villa Steno or Hotel Pasquale first. For a special occasion, you could also consider Hotel Porto Roca. You may never want to leave!
You'll also need to be aware that the towns become extremely crowded on days when cruise ships are in the area. The large groups from the ships inundate those small towns and it's not a pleasant experience (I can say that from experience). The easy solution is to be somewhere else between about 10:00 - 16:00 or so, or just relax in your hotel during that time.
In visiting that area, you'll first have to decide which of the five towns you want to stay in. Each of us here has a favourite, and I prefer Monterosso. It's the largest of the five and has the greatest number of hotels, restaurants and other tourist amenities. The other towns don't have hotels, but rather private rooms.
How long are you planning to stay in the Cinque Terre? I'd suggest three or four nights, depending on how many places you want to see in that area. For example, while staying in one of the five towns, you could also take day trips to Portofino or Santa Margherita Ligure (or other towns in that area), or take the Ferry from the C.T. to Porto Venere. For travel between each of the five towns, the local trains are the best option as they run often and the trip between towns is only a few minutes in each case. Levanto is only about four minutes north of Monterosso by train, and you could hike from there to Bonassola through the old railway tunnels (it's all paved so more of a stroll).
As you're in "great shape", you may want to do some hiking while there. Note that some segments of the popular Sentiero Azzurro trails have been closed for several years, and will likely remain closed in 2020. The segments from Monterosso to Vernazza and Vernazza to Corniglia will likely be open. There's an extensive network of trails in that area, so if you want to hike there are lots of opportunities.
To develop an Itinerary for the Cinque Terre and your other locations in Italy, you may find it helpful to have a look at the Rick Steves Italy 2020 guidebook (should be available now). Check your local library or local bookstores. You may also enjoy having a look at this - https://www.youtube.com/watch?v=WP316ABiTt0 .
How are you planning to get around in Italy? As yo may remember from your past visit, there are some potentially expensive caveats to be aware of when using trains and other public transit.