Hi Ryan,
Welcome back to the Disney Parks Moms Panel! How wonderful that you'll be able to travel to the most magical place on earth with your extended family!
I'm happy to let you know that yes, your in-laws will be able to make a
dining reservation for your entire group when their 180-day window opens. There's no need to wait for any stragglers! They'll simply find the restaurant where you're wanting to dine and make the reservation for the total number of Guests in your party. One of my very favorite things to do at the Walt Disney World Resort is to share a magical meal with lots of loved ones. You're going to love being there all together and are sure to make memories to last a lifetime!
I'm happy to hear that you have already linked together in your
My Disney Experience Family & Friends list. That will make planning your
FastPass+ selections together really simple, plus you'll be able to
view each other's PhotoPass photos!
Please let us know if you have any other questions as you're planning for your trip, Ryan, and have a truly magical...and delicious...vacation!
Missy