How about bring your mum and your son over to china as well?? If it's a big city like Shanghai or Beijing, I'm sure your mum and son will be able to have fun there and you guys can go out over the weekend.
But if that's not possible, 11 days is ok laa.. I feel your son will still remember you. I think spending time apart may not all be a bad thing. It also teaches your son that mummy will definitely come back to me.