What area of Colorado. What activities do you all do?
I would really recommend that you get a group site. It will be the least expensive way to go. Also, if you get 10 sites together you are going to have so much fun gathering at one or two sites for meals, campfires, chatting that you will be disturbing your surrounding neighbors.
A public state park might be your best bet rather than a private RV park. Some RV parks don't allow tents. There are many wonderful state parks in Colorado. Pick your area and call the park ASAP.