Rock Mountain National Park is one of the main attractions near Estes Park! A popular and beautiful very easy site to see is Bear Lake. There are town shuttles that can take you to Rocky Mountain National Park, or if you have a rental car you can see it that way as well! There are many other trails in Rocky Mountain as well, we would recommend using AllTrails to see what best fits the hike you are looking for. Below are the websites for the shuttles and All Trails. (As of now there is a timed entry permit need to visit the park between the hours of 9am-2pm, so if you plan on visiting the park during those hours make sure you go to the website and book that in advance!) https://www.alltrails.com/ https://estes-park.com/free-shuttle-buses/
There really are so many options for what to do in Estes Park, we can't list them all! This is a great website that has so many recommendations for things to do and places to eat. It really just depends on what you're looking for!