There might be some other RV Parks in Denver that have cable TV hookups, internet, and other amenities. I'm not an RV Park guy, so others will have to help you there.
I'd second (or third?) the recommendations for the Colorado State Parks.
Cherry Creek State Park is really close to the zoo. Cherry Creek is sort of SE to Denver city center.
Here are photos of each site at Cherry Creek.
Chatfield State Park is on a massive recreational lake, but has fairly barren landscape. It's sort of SSW of Denver city center.
Here are photos of each site at Chatfield.
Campgrounds fill up incredibly fast, cost around $30/night, and also require a $7-8 per day state park fee. Both state parks can be reserved via reserveamerica.com and reservations are on a 6 month window. Park entrance fees are paid on arrival.
Good luck.