Thoughts and Ideas to help Rehab non throwing broken arm

Hello. Avid reader of the forum and first time posting. I have a 10 year old son who eats, sleeps, and breathes baseball. Just 2 days ago, he broke his left arm skateboarding. We are currently in the beginning stages of the travel baseball tryout season and it’s killing him not being able to compete. Fortunately he has already secured a spot with a team based on his performance last year as a top of the rotation RHP and solid utility infielder. As such, any thoughts from the board on what baseball related activities he can do during his recovery to keep his baseball skills sharp? Also, what type of rehab “pains” can he expect after the cast is removed and he can begin baseball related activities again? Thanks in advance.