I think I would have done the same as you but our kind heartedness doesn't mean we would have done the right thing.
There's really no right or wrong decision, it's more of an ethical act on your part because, one way, the kid gets the deer,
the other way, you get the deer and it teaches the kid that this is what could happen with a poorly placed shot.
Not every hunter would give up a nice buck and I applaud your actions for doing so and I sure hope his dad points out to him that you didnt have to give him that deer.
Good Luck always