To see if there's an AP rate for your stay, check
here. Enter "APH" into the code field. If there's an AP rate for your dates at the time you're checking, it will show up. If not, it won't. But sometimes AP rates pop up later, so keep checking. (in the run-up to our Feb trip they showed up, went away, showed up, went away, etc many times)
You can book the AP rate without an AP in hand. If you find an APH rate that's great, book it, and then when you're closer to your trip, then buy the AP. I bought mine online, and picked it up at the ticket kiosk outside the gates. It was very easy.
If you don't get the AP rate, you'll have to figure out how much food and souvenirs your family will get; we get souvenirs, but our food budget for Universal is never hugely high. It would be hard for my family to justify APs for just those discounts (but we'd try anyway!).