As usual, state and national campgrounds do not as a group have full hookups and this is the case inside Zion. There is a park just outside the South Entrance to Zion that does have full hookups. Zion Canyon Campground is right next to the Quality Inn in Springdale. We walked through the campground and found it in unkempt shape as I had read reviews of the same on here. Although Zion River is probably 15 miles away (30 min driving through winding roads), I found Zion River RV Park much better. We felt so safe feeling that it was almost like a gated community in the park. We also backed up to the river, same as you can do at Zion Canyon. The trade off is the view at Zion Canyon was fantastic (those dramatic cliffs), however we also visited outside Zion (Kolob area and south of Zion), so Zion River proved to be better location.
It's a shame that the upkeep and service @ Zion Canyon isn't better, cause it's a killer location for Zion.