We feel you waste a lot of time and energy trying to drive back and forth between parks. It really doesn't take much to move to each area you want to explore. Plus, I'd hope you can plan on 2 or 3 days for each park. How often will you get back to them? Even doing some short trails will give you an altogether different feel of the parks rather than just skimming the top.
For Zion, there are full hookups just outside the park gate at Springdale. The free shuttle makes stops right in that small town.
For Bryce, Ruby's is the place to stay for convenience. Again, the free park shuttle stops there.
For Moab, there are many choices...just pick one. None of them are 'resorts'. It's just a place to sleep.
Use this site for finding RV parks:
Moab RV ParksHave a great trip....and don't rush it. :)
