Does, where you have already booked, have a shower/loo block and/or a Dump/fill station ? Water will be your main issue, especially as the small units can only hold a smallish amount compared to the larger RV units. The generator can be used when using a lot of power [observing silent hours] and using the RV during the day will recharge the batteries and shouldn't be an issue.

You can search for free dump stations in Moab area and if no luck, a lot of the other RV sites will let non paying guests use theirs for a fee.