Great to you and your crew for having a person with limitations. While going to ferry and especially when transferring to boat/ dingy, have 1 person ahead and one below to assist. Sorta the "dingy captain" philosophy. More assistance needed underway if the MS person is changing locations on the boat. At anchorage, less of an issue but you will see how comfortable and agile MS is on boat.
In this case, "An ounce of prevention is much better than a pound of cure" (i.e. falls are BAD). Have fun!