How much do you like to hike?  It's not possible to make a generalization without know what activity level you are looking for.  
For parts of Canyonlands, one needs a 4x4 and I don't know whether you have access to one.  One can rent for a day or two, but if you have your own, you can go a lot more places.
Also as noted, it is hot in the summer which restricts how much one can accomplish.  Give us some idea as to when you will be there.