I have only booked for Universal studios and the Grand Canyon 3 in 1 so far, as they are the only ones i really wanted to do. I will see how how i feel at the time for any others.
I also didn't want to book up too much in case there is somthing else i would rather do at the time.
I hope i'm not the only one doing the 3 in 1 for the Grand Canyon, it seem like most have gone for the skywalk.