Is she still going to be in the cast on 5/2? I broke my leg over the summer (tib/fib) and was only casted for 3 weeks. If so, I would reccommend getting the cast cover that allows you to shower and get the cast wet, even if it is just to put over it in case of a rain storm. Its kind of a pain to ensure that it stays dry, especially in the summer. Depending on the color of cast that she has, you could bring Sharpies and have the characters sign her cast.
I'm not sure if your daughter is into riding the coasters and wilder rides at the parks. I did not try any of the coasters since I knew what I was getting into and I was only 2 weeks post break so I wasn't riding anything too bumpy or jerky.