Hey there! Firstly, I'm seconding (or thirding, or fourthing) most of the stuff that's already been said - Get your ADRs booked as soon as possible; try and get as many of your staff on this board as possible, so they can ask questions, etc.
On the dining front, you may find that the resorts are the best place to have your group meals, as the CS locations tend to be a lot bigger there than in the parks. Of course, this does mean giving up a TS meal for a CS one (I think - I've never done any of the DDPs before). As others have suggested, it might be good to talk to the Grand Gatherings department, as they'll be able to point you to the places that may be able to accomodate your group, and can even make your ADRs for you.
When you split up into groups, you may need to have groups with mixed abilities, and challenges. As Juliah says, some attractions only have space for one wheelchair user at a time, so if possible try not to have more than one person in each group who is unable to transfer. Also, you'll need to balance the support-requirements of each group - you can't have a party with four wheelchair users who need to be pushed, if you only have two staff members with them

! This said, you might want to stick to Schmeck's idea of building groups based on each person's requirements, as much as possible - those needing closed captioning together, those needing audio description together, etc.
For all of your clients with mobility issues, I would suggest you consider some form of wheelchair or
scooter. Even if they are mobile enough to get around at home with a walker or cane, Disney takes a lot of walking, and they might need the extra assistance. I don't know exactly how you'd work this with transportation though, unless you rented from the parks each day.
For your clients with hearing impairments, Disney offers captioning or sign language interpretation for almost all shows and rides. Sign language interpretation isn't available at every show, all the time. Disney have a number of interpreters who move around between the parks and shows. You should be able to get better information on this from Guest Relations. The captioning is often done through a hand-held device, which can be picked up from Guest Relations at each park (you have to put down a refundable deposit for these, I'm not sure of the amount, though).
Disney have also recently brought out an Audio Description function, on the same device as the CC. This is still being rolled out, but you can find a review of the system as it currently stands in
this thread.
If any of your clients have sensory issues, and get 'overloaded' by load noises or bright lights, you might want to consider taking earplugs or ear defenders with you. A lot of people here who have, or who's kids have, Autistic spectrum disorders find that these really help on noisy rides; in busy, loud crowds; or during firework shows. Even if you don't think any of your clients will have problems, it might be worth carrying a few pairs of foam earplugs in your pocket, just in case the whole experience causes an unexpected problem for them.
Question for the floor: Does anyone know if Disney have brought back their special buses, with 8 wheelchair places on them? If they have, these would be a
huge help to you guys, but I know they were out of service a while back.
I hope some of this helps, and please do come back to ask any more questions you may have.
