At Haunted Mansion (HM) they will stop the moving floor and the Doom Buggies so you have time to get your dear wife (DW) in. I pull my
scooter up right next to the Doom Buggy and I can get in pretty easily. Same for exiting. My dear daughter (DD) will go get my scooter and bring it up next to the Doom Buggy and it's very easy for me.
HM is a very gentle ride. The cars are on a moving conveyor belt. And you need to go more than once, because there are so many things to look at, you can't absorb it all in one ride-through. It's tough getting on rides when you are handicapped. Some are impossible. What is especially nice about Disney is, those rides you make it on to, you can ask them if you can ride again, if no one is waiting for the handicap car when the ride is through. This goes for all the rides. Usually the answer is yes.
You mention a multi-family trip. Lots of people with lots of ideas of what to do next. I believe you and DW will slow everyone down alot. You should be prepared to break off into a very small group of your own. Especially since there are many rides (roller coaster-type) that you must pass on. Keep a cell phone on you and try to meet up at key times. For counter service meals, I will usually find a table and DD will get the food. It is a bad idea to enter a counter service line with a scooter, unless it is marked as a handicap line. You will get stuck and have to back up.
There are specific handicap places for parade watching. They are marked on the maps you pick up at entry. Of course, you can always ask a Cast Member (CM). There are many family bathrooms in the parks, big rooms where your DW has room for her scooter and for an assistant, if needed. They are also marked on the maps.
Here are park maps and resort maps:
http://www.wdwinfo.com/resortmaps/
WDW is tops in accommodating the handicapped. That's why we return again and again.
