If you do end up doing Antelope, do the lower one. When I was there, I had a tri-pod and they gave me a photo pass and I walked around by myself for 3 hrs. Seemed way less crowded than upper, and a lot more fun of a canyon to hike in.
Depends on how far uplake you go, but Wetherill and Mountain sheep canyon are very fun to explore. They are near Dangling rope Marina on the south side of the lake. And depending on water level, there are slot canyons at the end you can walk up for a ways.