RE: The most fun I've ever had!
That is a great buck! Your son deserves to be proud of that one.
As far as spoiling him, I don't see how taking your boy into the woods to harvest a deer together could ever be considered spoiling. Like you said, he's excited about hunting. But hunting with your dad is even more exciting.
You're telling him that these kinds of mature bucks don't come around too often, so he knows better now. It's important to be grateful for the deer that we do encounter, and each should be equally exciting in its own way.
Good luck to the both of you in future hunts!