Hello there Sarah,
Welcome to planDisney and thank you for your question though I'm terribly sorry to hear about your son! It's never good timing for a kiddo to get injured but it certainly makes it more stressful when it's before a big trip.
I want to state upfront that I'm not a doctor nor am I qualified to give any medical advice. Therefore I would start by saying you should absolutely discuss this trip with your son's doctor to get a really clear picture of what he can and cannot do during his recovery process.
As I mentioned in
this answer for another Guest with a similar situation, many of the
attractions at the Disneyland Resort - even the overall gentle ones - have quick stops and turns that I could see being painful for your son depending on where he is at with his recovery. Therefore, it'll be important to ask your doctor what to avoid during your trip.
If your doctor advises that he can go on gentler rides then you could stick to more gentle attractions like those found in
Fantasyland. Additionally, there are still plenty of other things to do during your visit like
character experiences, parades and other entertainment, as well as enjoying all the fun that comes with
Pixar Fest if you'll be visiting before it ends on August 4.
Thanks again for your question, Sarah, and I wish your son a quick and easy recovery!
Have a Magical Day,
Greg