4 day cruises are operated on older ships, which don't always have totally wheelchair accessible cabins. I would have your travel agent check this very carefully for you. On a last minute booking, my grandson and I were in a wheelchair accessible cabin and it was perfect. Big,k huge bathroom, located on a large corridor with other wheelchair accessible cabins, fold down seat in the shower and a brace by the toilet, mirrors that could be lowered, clothes racks in the closets that could be lowered, really amazing to someone who isn't familiar with that type of cabin. If your family could stretch out your cruise to 7 days (4 days plus the weekends you know), you could sail on a new ship and know that there would be no problems at all with wheelchairs.
Carole