What to do in Colorado?

I am going to Colorado ( highlands ranch/castle rock area) and will be staying with my sisters for a couple weeks for some R&R. She asked me to let her know of some activities I would like to do. Money is not a problem but I am in a wheelchair so no hiking or anything like that. I can walk a little ( like 1 block) but that is on a good day. Please let me know of any ideas. Denver is also an option. Thanks!