Hi, Kristin! It's always a pleasure to help a fellow Pennsylvanian here at the Disney Parks Moms Panel.
Like you, I am also the parent of a child with
special needs. My son has autism, and when we visit the Walt Disney World
theme parks, we also use
Disability Access Service (DAS). In my experience, whenever we have visited
Guest Relations to set up Disability Access Service for my son, everyone in our party needed to be present to have their
MagicBand scanned to be associated with the Disability Access Service account. I would think that it would be at the Cast Member's discretion as to if he or she would be willing to scan your MagicBand to add you to the Disability Access Service account without you actually being present.
I would hate for the rest of your family to make a special trip to Guest Relations and be unable to set up Disability Access Service, so I would recommend waiting until you can accompany your family. Registering for Disability Access Service is a simple process that can typically be completed quickly, so hopefully, it won't be too much of an inconvenience to wait until your entire family can visit Guest Relations together.
As you are getting ready for your trip, you might want to check out this
Guide for Guests with Cognitive Disabilities. It has some great tips for visiting the
Walt Disney World Resort with someone who has special needs.
Wishing you miles of magic for your
runDisney race and a wonderful Walt Disney World Resort vacation!
Samantha