We like to do rides where everyone can participate, too. We have a short 3 yo and a 1 yo. We found lots of things that the family could go on together in every park but AK.
I know several people have done preview rides of Mission Space. I didn't even attempt it when I was there because DH and I both get motion sickness from rides that spin around fast like that. I have read several posts that MS is not for people like us, and I definitely wouldn't want to chance it with the 3 yo, even if he was tall enough.