Welcome to the Disney Parks Moms Panel Laura! Thanks so much for sharing your question with us! Your family vacation sounds amazing and I know you are going to make countless magical memories!
This is a great question and I love how proactive you are being with your planning!
Guests staying at a Disney Resort hotel can begin making
FastPass+ selections 60 days in advance. You will be able to make your selections a day earlier than those in the second room. You can either wait one day and do everything at once or you can make your selections at the 60 day mark and then make theirs the next day. If needed and available, you can adjust your times to match theirs if you cannot get the exact times. We have done something similar in the past and our selection times started within a few minutes of each other, so it worked out well.
As you are making your FastPass+ selections, I highly suggest
Avatar Flight of Passage as a must do attraction! You will soar on the back of a mountain banshee while enjoying the majesty of Pandora. The 3D experience is breathtaking from the very first moment!
Thank you, again, for sharing your question with the Disney Parks Moms Panel. Please let us know if you need any further tips as you plan your family's magical Walt Disney World Resort vacation.