Welcome to The Helpful Gardener. Don't be too hard on your son, we have all done foolish things. I once chopped down a beautiful old Cherry tree, no kidding. I would absolutely expect that you will get some some new growth from the stump. In bonsai we often do this sort of thing. The real question is what type of tree will arise from the stump.
Often Japanese Maples are grafted with the named variety joined to an understock of a different variety. If this is the case, and if the new growth emerges from the understock, then you can not expect the same variety that you previously enjoyed. If the tree was originally a seedling, or a cutting, then there is no understock to be concerned about and the new growth will be the same as the old. Also, even if it was grafted there may still be some of the named variety remaining.
Do you know if it was grafted? Look for a different color or texture of the bark, often in the shape of a V. Unless you truly want it gone, or want the space to replant, I think I would leave it see what happens.
Do you have any interest in bonsai.