You got a lot of good ideas.
This may be the time for her to learn about being quiet, listening, entertaining herself, etc. All children no matter what age, need to learn this skill to some degree. At her age it is only going to be minimum, but she still needs to know how to be able to sit in a chair and listen to someone for 5 minutes.
I had a rowdy one and I know how hard it can be at times. I would think she would be on pain meds at this point and they would be calming her down? When our son broke his arm he lay around on pain meds until he got his cast. Those meds kept him pretty quiet for the most part. He watched tv, listened to music, read, and slept. His was a bad break also- both bones in the forearm. And they want bad breaks to be as still as possible because of the bones shifting around. ugh
Oh, be sure to call beforehand and make sure about how they are going to set it. I was not aware of it, but recently someone told me they will heavily medicate young children to set bad breaks (avoid the trauma,pain, and fear). Therefore the youngsters cannot eat breakfast before the procedure. So you may need to call and check on this.
After the cast. I would look into preschool for this fall. ;-) All kids love to be around others their age. She would still learn a lot, get to move around more and you could get some rest. Once she has a cast and crutches she is going to be going as much as she can, I think. LOL If you have a good teacher, she will just take it in stride and keep going.
Good luck