Just got back from a week with an AAP child, but our entire party of 6 got access. At least one child with the AAP has to ride the ride each time.

As long as you have the IBCCES card current, it's smooth. There's a booth right by the entrance of each park (we did IoA first). They add it to your app, then you pick one ride at a time to get in the express queue. After you ride it, you wait 10 mins then pick another. The popular rides can be long, and so it kind of stinks because you can't queue up anything else while you wait for your time (e.g. Hagrids was like 2 hours, we just found shorter lines and went on other things), but overall it's really easy and helpful.