Colorado

Estes can get pretty crowded during peak of the summer season. We usually find a place west of town to escape the hordes - out along either Rte 34 or 36, which is a lot closer to the park entrances anyway.
RMNP is one of those places getting loved to death, especially during the peak summer months. My advice is to get an early start, ie as close to the crack of dawn as you can manage. That way you'll beat the crowds and arrive at the trail heads in plenty of time to secure a parking space - parking is limited and fills up in a hurry after 9 AM. You'll maximize your chances of seeing wildlife too if you're out early, plus you'll beat the heat of the day. It's surprising how warm it can get up there, especially if you're horsing along with a backpack. Bring plenty of water on your hikes.
Going out later in the afternoon is also an alternative, but then you'll have to worry about late afternoon thunderstorms which are not to be taken lightly in the mountains.
On our most recent visit we stayed on the other side of the park in the town of Grand Lake, which is a cute little place and which didn't have nearly the crowds of EP. Fact is we'll probably be staying over there from now on.
The RMNP website has some excellent maps of all of the hikes. I wound up using those more than the National Geo Topo map that I bought several years ago.
The trails within the park are at an altitude of 10,000 ft and most require some climbing- you're in the mountains after all. Point being that you'll need to pace yourselves since you won't be acclimated. We live at 7,000 ft here in the Springs and even we do a lot of huffing and puffing for the first few days. It's worth it though - Rocky Mountain really is one of the crown jewels of the National Park system. We try to go every year. You'll love it.

I've stayed at Estes Park many times but almost always off season, well at least what used to be off season. Love it there in October. If you really don't like crowds and you're there during the summer, I agree with Robert that Grand Lake is a nice place to stay, I've stayed there twice. The only issue with Grand Lake is that it takes a bit longer to get to the most popular spots in the park than it does from Estes so you might have to leave a bit earlier if going to hike the most popular hikes (Bear Lake, Gem Lake, Emerald Lake). But, on the other hand, that side of the park is way less crowded and better chances of seeing wildlife.

If you have the time, I'd bump out the route to cover Maroon Bells near Aspen, Colorado National Monument, and Black Canyon of the Gunnison National Park. Don't get me wrong ,we really enjoyed our time in Rocky Mountain NP, but found that part of the state to be a little more unique and interesting.

I am one of those locals that is not the greatest fan of Estes Park. Estes Park and Gatlinburg are not that far apart although Gatlinburg is much larger. The RMNP and the drive over Trail Ridge Road is spectacular but do it on the way to somewhere else. Time it so you do it on your way to Steamboat. IMO, EP has little to offer beyond t-shirt shops and ice cream stores. Upscale is not a word I would attach to EP. The exception is the Hotel Stanley but it is a quick hit.

From Steamboat you might consider a loop though Glenwood Canyon, Glenwood Springs, Aspen, and out the back side over Independence Pass to Leadville. One of the hidden gems is the Mineral Belt Trail -- 12 miles loop, hard surface hiking trail into the old mine section outside of historic Leadville. And then find 70 back to Indiana.

Just east of the tunnels is Georgetown. The only remaining territorial city in Colorado. Worth a couple hours stop and a tour of the old hotel. And a great ice cream shop there also. The Georgetown Loop Railroad and especially the silver mine is very interesting but a bit touristy. But we do it every other year or so because it is run by the Colorado Historical Museum and we get free tickets every year.

A nice micro-brewary in Idaho Springs for a final beer in the mountain. And if you really want to top it, before hitting the flat lands. Have dinner at The Fort in Morrison overlook the Denver. It is expensive but worth it. From the patio with sun sitting and lights coming on in the Denver metro area, it is a very pleasant way to end your Colorado mountain trip.

Thank you all for your opinions. You have given me lots to think about! I love the planning stage 😊

There is some very detailed information on the TripAdvisor Estes Park forum (and the TA Colorado forum) about Estes Park. Where to stay, when to go, how to navigate through the crowds, hiking suggestions, etc. There are some very informed and helpful people there. I suggest reading some of the existing threads before posting a question of your own.