Maybe this only applies for larger groups, but you need to make reservations well in advance (at least a year for the Scout troop, IIRC). They only have so many camping spots, and it is a popular place. But if it's just a couple of you, maybe you don't have to make reservations so far in advance. I'd look into it, though.

But if you're into the camping and outdoor recreation, the Arches/Zions National Park trip is always good. You could probably fit in Bryce Canyon as well. I've never been to Canyonlands, but they have some good hikes as well (I've heard).