I've been coming to Estes Park and the RMNP for years! I'll make a few quick suggestions.
Check out the YMCA of the Rockies. If you can get a cabin or a lodge room there, there are many great services included. They offer many guided hikes ranging from half mile bird watching hikes to 15 mile ""14er"" hikes! They also have many concerts, shows, classes, bike rentals, sports equipment, arts and crafts and much more! They even have a day camp for all ages of kids.
If you hike (which you should), be sure to check out The Loch, Ouzel Falls, and Bear lake. If you have time to hike up to Lake of Glass and Sky Pond (up the trail a few miles from The Loch) do it!
Lastly, spend time in the town of Estes Park. There are a ton of great shops, amazing restaurants, fabulous people!
Pros: beautiful views, lots to do, affordable fun
Cons: parking
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