And Arches and Zion are very hot. Bryce will be cooler and has excellent hiking. The CG is also good.
Canyonlands is mainly a park you drive around, there are some fantastic overlooks. Ask at the ranger station. Camp at Deadhorse state park for Canyonlands and if you go to Arches.
Zion CG is also very good, right on a river. Go hiking early in the day, the hikes can be strenuous. We really liked Hidden Canyon Trail but it is what climbers call exposed, you go part way on a hanging shelf maybe 6 ft wide. So fear of heights eliminates this one. Zion Narrows is probably one of the most famous hikes around, bring water shoes since it follows the river in the river. Don't go w/o checking with rangers about weather.