Why doesn't your current doctor support home schooling and when is the surgery scheduled?
I know that most states have guidelines on homeschooling... do a general web search under "homeschool" and see if you can find anything about your state's guidelines.
I'd like to hear more on this... I think maybe you could ask for a referral to a psychologist in the meantime and have the child evaluated concerning the damage emotionally of having the child attend school right now. While I don't propose just keeping the child out, perhaps a psychologist could intervene with the school on your behalf and find a way to work this out.
This would only add to your stress...
This is also where you need to take care of YOU! Rose, call for some help... call your church, your neighbors, your friends, your relatives. Tell them you need help. People want to help, usually. They just have no idea what to do. Ask a neighbor if they could possibly cook a meal once a week and bring it by. Ask for some help keeping the house up. I'm willing to bet that no one really knows how stressed you are. Ask someone to babysit and take the child's mother and yourself out to a spa!
It's humbling, I know, to have to ask for help. But so many times people really don't know what kind of help you need. They're all out there, waiting to be directed.
If you, as the grandmother, and the child's mother don't take care of yourselves, how can you take good care of the rest of the family? I'm willing to bet that there's a whole support system out there for you... you just haven't told them what you need.
Best of luck and let us know how things turn out.