Colorado near Estes...what now?

We will be meeting friends for a week in Estes Park beginning Sept 23. Got a chance to head out a few days early so almost to the Colorado line and wanting input on where you'd go near Estes if you had an extra 5 days. We would love a quiet campground on a lake to chill and use as a base for day trips to sightsee, hike, and explore. Any of your favorite RV parks fit that?