Package tickets can't be upgraded until you have checked in so if your tickets are part of a room+tickets package, you'll need to remove them from the package and buy APs separate. (You could buy the AP first then remove the package tickets.) Removing the tickets will leave you with a "basic package" that is essentially a room-only with package terms for payment and cancellation.
If your tickets were purchased separate from the room reservation, you can upgrade those. If it's like last week's DVC release you'll need to call to upgrade to APs.
@scrappinginontario answered about
Genie+ and ILL$. I think there were some issues early on buying Genie+ for a group with mixed tickets (AP and regular) -- I haven't followed whether that issue was resolved or not. But as for booking rides while in the park that day, it shouldn't matter what ticket type.