Hi, Mary! Thanks for bringing your question to the Disney Parks Moms Panel.
One of the things that I love most about the Walt Disney World Resort is how they go above and beyond to make sure every guest has an experience that is practically perfect in every way. Whether a guest has a physical or cognitive disability, Walt Disney World provides services that make the magic accessible to everyone. My own son has autism, so I know from personal experience how welcoming and inclusive the Walt Disney World Resort is for those guests with special needs.
Walt Disney World's
Disability Access Service is intended to help guests whose disability prevents them from waiting in a conventional queue environment. When you arrive for your first day of fun at one of the Walt Disney World theme parks, you will want to visit Guest Relations with your entire party to discuss your specific needs with a Cast Member. You can find a detailed description of the process for obtaining Disability Access Service by using the link I have provided in this answer.
If it is determined that Disability Access Service is right for your girls, I would suggest that you obtain Disability Access Service for each of them. When utilizing Disability Access Service at park attractions, the guest that the Disability Access Service pass is issued to must be experiencing the attraction. So if your girls might want to visit different attractions with different adults in your group, they would each need a Disability Access Service pass.
Wishing you a magical, pixie-dusted vacation!
Samantha