You pay the difference between the AP you're getting and the "upgrade value" of your ticket.
Right now the Premium AP is 379, the Deluxe is 259. I don't know about the southern CA ones.
If you bought your tickets and that's it, you probably paid the cost they'll go from. If they were part of a package, you won't know their actual value, but you could probably call
AAA and ask what their value was.
It's encoded on the tickets, to the AP office will know.
When we went, we had 5 day tickets from our Costco package. The adult tickets were valued at 189, so we paid the difference between that and what the Deluxe was at the time (we upgraded the day before the prices went up to what they are now). With DS's it was a bit more, b/c the AP cost is the same from 3 to adult, but the tickets were worth less.
Are you staying onsite? If yes, you can upgrade any time. If you're staying off site, use your Magic Morning first, and then after that (even on the same day) you can upgrade and not lose that MM day Take everyone to the AP office, wait your turn, give them names and address, they take the tickets, you pay the difference, everyone gets their pictures taken (they can take pictures of kids in strollers), everyone gets their APs!
