Hello everyone

I have been reading a lot on this forum and learned a lot but I need a little bit more help.

My girlfriend and I have now decided to do a road trip within our a 2 week holiday in the US in April, for app. 9/10 days (starting on the 12/04/2011) through Utah.
Our itinerary would be the following:
- Arrive in Las Vegas
- Zion National Park
- Bryce Park
- Monument Valley (may be going there through Capitol Reef as the road seems great but apparently we will have to avoid Moab because of the Jeep Jamboree week)
- Page Antelope Canyon / Grand Canyon (South Rim)
- Las Vegas

We plan to do this trip driving an RV.

My questions are the following:
1/ What is your view of my itinerary (do we have enough time to do it or actually could we see even more (do we miss something essential))?
2/ How long should we spend at each destination (we like hiking but we don't plan to do "hard core" hikes))?
3/ Is this trip do-able with an RV (could we have problems on the road (bad quality of the road, snow...), would that be too cold to stay at night in the RV?) or should we rent a 4x4 car and find motels at each destination (is a car better to use in the parks)?
4/ If we go for the RV, do we need to book camps in advance because of Easter break or we should be ok if we call a few days in advance, and do you have good address for RV rentals?

Many thanks for your help

Nils