We have a trip planned in 22 days, yesteday grandson ,7, broke his arm. We don’t have any of the big roller coasters planned, but 7DMT and FOP to name a few. What do you all think, are there rides he shouldn’t or couldn’t go on?
DD5 broke her leg 2 weeks before our disney trip in June. She rode everything. She just couldn’t walk. 
Depending on the cast (short forearm only or full arm), I don’t think there will be too many restrictions. If he has the short cast, hopefully a waterproof liner so he can swim!! I think 7DMT should be fine as it is pretty tame, he will have one hand to hold on with (if needed) and an adult can certainly help steady him if necessary.
Honestly, I would leave it up to him to decide how he feels about trying different rides. Things requiring mobility might be more difficult (think steering a car on the Speedway), but I would guess that with one good arm he could do most things.
I can’t remember how much holding on is required for FoP, but I bet he wouldn’t be the first person to ride with a cast!
You should check with Disney about rules they have for casts on rides. I remember being turned away from coasters at Six Flags b/c of my arm cast one time–it was a hazard for those sitting near me. I can see how it would be different with a leg cast.
p.s. very sorry to hear that, by the way.
Aside from anything Disney might suggest, I think you might want to shy away from the Tea Cups unless it is kept pretty mild. Generally need to hold on for that thing! I’m not sure if the Alien Space Saucers might have the same issue since I haven’t been on it.
as additional help check out the following:
Disney Mom panels usually echo the company line… it doesn’t look like WDW has any rules per se, as the answer simply is to talk to doctor and follow doctor’s advice.
Is he in a cast? My son broke his arm right before our trip in 2015 he did not have a cast just a sling. We rode all the rides including coasters and he was fine.
Sorry to hear that happened it is a bummer right before a big trip but it doesn’t have to ruin it 
This might be helpful:
Thanks to all who replied! I appreciate the help, it looks like we won’t have to change too much.