Here are two in Estes Park that you will love: Elk Creek Campground. http://elkcreekcamp.com
Small, nice privacy between campers. Close to two large lakes and entrance to Estes Park. The other one is Winding River Resort. http://windingriverresort.com
Larger, but great horseback riding and overall the best in area. Perfect for kids and not like the KOA nearby.
We are always staying at new places in Colorado so will keep you posted.