I assume that this Minor's license is a Minor's PAL.
IDPA won't care about that anymore than they will ask for your own PAL or any other number. They assume that you and yours have met any and all legal requirements for your location. So they'll happily welcome you and your son into the fold....
You are both in for a lot of fun.
Both of you will need to get set up with holsters and begin getting familiar with them. I'd suggest that you each "Safety Officer" each other during a LOT of regular unloaded handle and holster sessions at home.
It's important and helpful to learn and practice a safe holster draw and to work on your trigger finger discipline before you get to the range. In particular to conciously be aware of NOT putting your trigger finger into the trigger guard until the muzzle is at least 45 degrees away from vertical. Lots of repetition and lots of practice sessions ahead of time is the key to imprinting these habits into you and your son. And since IDPA does not have any sort of "Black Badge" course self training is a rather valuable idea.
It would not even be a bad idea to have a little "dry fire" mini course in your basement. You and your son could practice all the calls and procedures from the IDPA rule book and get used to them all well before your first match. It'll aid you both in learning to "face downrange", "load and make ready" and then to be watched carefully during the draw following the "beep" from the SO. The "shooter" would draw and dry fire at the first "target" and then move to a new position while being watched for safety infractions by the other. It can also be good practice for the whole first shot process of draw, join in the support hand and push the gun out while gaining the sight picture that is all so important to a good first shot.
Punishment for trigger finger infractions should be suited to each of you. Like 5 pushups in your case and 25 in his?

That and the very real but unspoken realization that a trigger finger violation in entering the guard too soon on the draw COULD have been a hole in the leg or foot. The sport is all about fun. But it's about having fun SAFELY and realizing that we are playing with stuff which can seriously hurt us if we don't make this automatic discipline an integral part of how we handle our guns at all times.