Just book what you would book as a family without disability. You are a family of 4, so you can book any room type that would fit 4. For the moderates that would be all room types apart from the specified king bed type rooms. (read; this is something else than booking a standard view, water view, preffered, or pirate room in an accessible mode)
If the bedding are different because of the fact that you need an accessible unit, WDW will take care of it. They have multiple ways of taking care of it and some of us don't feel comfortable naming some of those for everybody to read, but you will be taken care of. There will be room for the 4 of you to sleep properly, just like any other family without disability would have when booking a room that fits 4.