You're a great dad! I didn't mount my first buck but I still have his rack hanging on my basement wall with a nice picture we took back then. I still wish I would have gotten him mounted but at that time my dad must have not wanted to fork out the dough!
The way I see it, years down the road he'll probably have some nice size bucks on the wall, but everyone will always ask what the story with that one first off! I always look at my first buck and smile, and for the thousands of dollars ive spent on the addiction from then on!