I really enjoyed my bed and breakfast. The host was awesome, knows more about moab mountain biking than probably anyone. Happily works on your bike when you get home so you don't have to bother going to the bike shop to adjust something. Helped me plan rides. Fed me breakfast. I think it was $100 a night too and you can ride bikes to town.
https://www.facebook.com/pages/Roost-Wrench-and-Ride/351892251505533
Ashley (mom) really liked the one she spent a night in as well.
http://www.launchpadmoab.com/
same deal, total moab knowledge.
Car rentals are monumentally cheaper in Vegas. you may consider adding that, a cheap night in vegas, a day in Zion. It's ~5-6 hours away total. Zion is cool as hell.
IIRC the bike rentals in Fruita were a decent amount more money.
I just did 10 days and it wasn't enough out there. Would certainly go back next year. You should plan your trip for Sept next year and we'll all rent a house together. I know Tim and Ash would totally go back again.
Seriously consider borrowing a full suspension bike and riding Cannonball and top of skyline a BUNCH OF TIMES to get yourself prepped for the trails out there. There are easy trails, and the "normal" trails aren't crazy hard, they are easier than Cannonball but you'll really want to familiarize yourself with using the suspension on a full suspension bike, and dealing with riding around a 6" travel bike.