Here a web site for park sleep and fly but can't find any of about accessibility but they are required by federal law to have accessible shuttles you just might need they them know your flight info so they put that one on the run. Here in NYC by grand central they have bus to all three airports and seems that almost every other shuttle bus is accessible or their at least one parked their every time I walk by and they don't require advance reservations so they have to be prepared plus they are good priced for where they set up shop.
If the hotel has a shuttle to airport most likely they will have an accessible one or if they use a service they will have to have one not everyone required to be accessible but not sure how many to a regular shuttle bus/van.
I never used that site so use the ones you like a loft are supposed to be nice never stayed at one yet but they are owned by a good company.
http://philadelphia.parksleepfly.com/