Hi, Ann!
Welcome to the Disney Parks Moms Panel and thanks so much for sending in your question!
Wow! Ten nights at the Walt Disney World Resort sounds like the best vacation EVER in the making! And how fun that you'll have different family members joining you for parts of your vacation!
If the 2 people joining you for the last 5 days of your trip have their Park tickets, they will be able to make their
FastPass+ selections 30-days in advance. I know that doesn't help for making them 60-days in advance, but you can just try to get similar selections around the same time so you can all ride together. With the FastPass+ still testing, something may change between now and the time of your vacation, so just keep checking in.
I sure hope this helps, Ann! Please don't hesitate to write back in if we can help with any other questions you have as you continue to plan.
Wishing you and your family a Pixie Dusted vacation!
~Jackie