This movie was split in half for me. I loved the prank scenes like always. Some were simple and the reactions to them made me laugh my ass off. These were the types of things that I always loved about Jackass. Some were a little gross and/or sexual but they were much more tame than usual so I even enjoyed those. The only bad thing about the movie is that instead of a series of pranks, they tried to make it an overall legit movie about the grandpa bonding with the son. So any time they were on that track, I found myself bored and just wanting them to get back to pranks becuase these two characters are already established as fictional masters of prank. Why would I feel any sort of emotional connection to their "story"?
I would still recommend anyone that likes the Jackass show/movies check this out because there are some really big laughs in it. Just be warned that this is a lot more like Dictator with Sasha Baron Cohen where the "story" of the movie gets annoying inbetween the laughs.