Hi Kayla,
Thanks for visiting the Disney Parks Moms Panel for help planning your upcoming Walt Disney World Resort vacation! Disney trips with extended family members are extra fun! You are sure to have a wonderful time and make many memories with your mother-in-law. As far as your
Advanced Dining Reservations, one of you will want to make the plans and include everyone in the headcount. This way, you will all be seated together when you dine. When booking your dining, you can begin doing so 180-days prior to your arrival. Be sure to link your resort confirmation number through your
My Disney Experience account. Once you do this, you will be able to begin booking at 6:00 A.M, exactly 180-days prior to your check-in day. You can make reservations for up to 10-days at that time. You will also want to be sure that you and your mother-in-law are connected to each other through your "My Family & Friends List" on your My Disney Experience account. This will make it easier to book Advanced Dining Reservations and FastPass+ times for everyone in your party.
If you need any clarification or further assistance, please do not hesitate to send a follow-up question.
Wishing you magical memories,
Kaylene