Hi, Cheryl! Mickey and I are sorry to hEAR about your son's broken arm, but perhaps he can be an honorary "Cast" Member when you travel to your happy place next week!
I emailed Guest Services, and they confirmed that there are no
ride restrictions as long as the cast doesn't affect the harness/safety bars on the attractions. That being said, I'd encourage you to check with your son's physician to see if they recommend any safety precautions before traveling. Unless he has a waterproof cast, you may want to avoid water rides, such as
Splash Mountain and
Kali River Rapids. The only other attractions that might pose some difficulty are
Toy Story Mania! since the spring-action shooter needs two hands to operate correctly, and
Rock 'n' Roller Coaster, unless he's okay with holding on with only one hand during the white knuckle inverted loops! Former Disney Parks Moms Panelist,
Linda, also offered this great suggestion: If there are any attractions that you are particularly concerned about, watch some ride through videos online to get an idea of which attractions he will be comfortable riding.
I hope you have a magical vacation next week, Cheryl! See ya' real soon!
Eean