I foster broken pups all of the time. The most important thing is to follow the vet's instructions. The pups always seem to handle it pretty well. I have never had a pup with bilateral fractures; but I did have one who had to have surgery on both hips at the same time. I was really surprised at how well he did. They have such amazing spirits.
I think the most difficult part with this one will be keeping him quiet since he is so young; but it will be so important for his well being.
Good luck if you decide to foster him.