Do you tow a car?
I agree...stay in the Park. Sunrise and sunset provide beautiful lighting to the Canyon. You could exit the east road, then turn south on Hwy 89 and check out Bonito Campground, a nice Forest Service cg at the entrance to Sunset Crater Nat'l Monument. No hookups, but paved roads. It's a few miles north of the east end of Flagstaff.
The only RV park actually in Sedona is Rancho Sedona. Central location in natural trees by the creek, but a bit pricey. Dead Horse Ranch State Park in the nearby town of Cottonwood is also great. Or some people enjoy staying at Distant Drums RV Park along I-17 south of Sedona. That one is near a casino and Montezuma Castle Nat'l Monument.