That's very cool, congrats to you and your son!!!
Ive never caught a ball at an MLB game but when the Pacific Coast League was in Calgary, Alberta back in the 80's and 90s, we were the AAA team of the Seattle Mariners and as a kid, in the age range of 10-15 years old, me and my friends would often wait (probably 30 or 40 times a year or more, lol) in the HR territory at these AAA games with our Baseball gloves to catch the HRs and some foul balls that would come into the field beyond the stadium.
The best HR balls i remember getting were from Danny Tartabull, Tino Martinez and Alex Rodriguez. All players that played their AAA ball in Calgary and i still own those balls to this day (they are somewhere around here, lol). I even got the Tino Martinez ball autographed.