Hi Joshua!
Thank you for bringing your question to the Disney Parks Moms Panel.
The Advanced Dining Reservation you have already created and the
Rivers of Light Dining Package are actually booked through two different systems that have different availability, so unfortunately you cannot upgrade your current reservation. I would recommend checking first to see if you can still book the Rivers of Light Dining Package before cancelling your current reservation. This way if it's available that's great and you can cancel the regular Advanced Dining Reservation, but if it's not you won't lose your current reservation at
Tusker House.
To book the Dining Package you can
check availability online or you can call 407-WDW-DINE. Since it will be linked to your
My Disney Experience account it will not allow you to hold both for the same meal time so I would check the availability, if it's there you'll need to quickly cancel yours then immediately go back in to the claim the new one.
I've heard wondEARful things about the new show and I thoroughly hope you enjoy it! Please let me know if you have any other questions before your trip.
-Lindsey ºOº