It's good that it's just a little boy thing to be honest.Some boys will wet the bed until puberty. They simply do not have control of the relevant sphincter / muscle (I forget the details). The medical term is nocturnal enuresis. You may find that waking him at eleven or midnight for a **** helps. The important thing is to not criticise him or stress him about it. He physically cannot help himself. Just get on and deal with it.
Just trying to get home to go to the toilet is a chore.