If you're making the reservation online, when you add the package to your cart you can adjust the number of days on your ticket. If you make the reservation over the phone just ask. Days 5-10 are inexpensive to add. If you've already booked the package, just stop by guest services at one of the parks or Disney Springs BEFORE you use the last day on your ticket. You'll be able to upgrade and they will reduce the amount owed by the amount already paid.