I am overweight and am disabled and have been on ten cruises since becoming disabled. Handicapped rooms are best, but as long as the showers have curtains and not doors I am okay. The chairs in the dining room are okay as are the theater chairs on every RCI and Celebrity cruise I have been on. We scout out the theater first thing and find the best seats and get there early and usually get our favorite seat. The lounges have great seats especially the Viking Crown on RCI ships. Your father will find some problems with the life vest but they will fit him. Of course I wouldn't want to test it out in the water to see if it would keep me afloat,lol.