This battle is a long one. It starts out with the three of you battling Kid Buu. With that many of you all going after him, he shouldn't be much of a fight. The next phase has you protecting Goku ...

Kid Buu is quite strong, but with Gohan here, you shouldn't have many issues. Buu will autogaurd quite a bit, so if you have beam attacks, use those as they are very good at punching through it.