Greetings, Monica!
Welcome to the Disney Parks Moms Panel, and thanks for your question. Like your son, my son also loves PJ Masks on Disney Junior. In fact, last year he was Catboy for Halloween!
While our kids do wish there was more PJ Masks representation in the parks, unfortunately I haven't seen any Characters to meet or merchandise to buy specifically for PJ Masks there yet. I have actually been able to find the most PJ Mask merchandise for my son at our local Target store. Here we have seen clothing as well as toys with his favorite PJ Masks Characters.
If your son is like mine, then I'm guessing he may watch some other popular Disney Junior shows as well, which means he will just LOVE the
Disney Junior Dance Party! located in Disney California Adventure Park. Outside of this theater, you can also spot some Disney Junior Characters meeting throughout the day. Just check the
Disneyland app each morning so you can see who will be meeting. We recently met Fancy Nancy, and my son thought she was just delightful. Don't forget your autograph books!
I hope this helps, and please return if you have any questions.
-Jennifer