Congrats on getting your pool sessions done! You're almost there!
As for your son, if he's done the Bubblemaker dive, maybe consider signing him up for the PADI Seal Team. It's basically the open water pool sessions you just completed. They will teach him essentially the bascis of scuba in confined water so when it comes time for him to get certified he'll be a little more comfortable with performing those skills (mask clearing, reg recovery, fin pivot, etc.) and be a step ahead of the game. And if he enjoys that, then he can do the Master Seal missions, which will introduce him to things like wreck dives, night dives (they turn all the lights out in the pool and give them a flash light), search & recovery....there are 10 missions total that he can do one at a time. My son will be 10 in September and he's already counting on getting his OW cert for his birthday. He did the Seal Team missions over the summer and absolutely loved them! He actually did better with mask clearing the first time than I did when I tried it my first time. And it gave me a chance to see how he conducts himself underwater with respects to how to handle things like a flooding mask or having to find his reg. It really showed me how comfortable he is in the water and how well he can comprehend the concepts of scuba. Obviously not as well as an adult, but at least enough to where he can safely operate a scuba kit under supervision. And I think getting him certified early in life will make him a better diver later on. Kids are enthusiastic about things. They get excited. I've decided that if I ever decide to become an instructor I'd want to teach kids for that very reason.
So maybe consider getting him in the Seal Team program. If he liked the Bubblemaker dive he'll LOVE that!