I (65 yr old male) take 2 Pilates Reformer classes/week and work out at our gym 3 other times per week and walks our neighborhood 4x week.
My wife (62 yrs old) dances in a Senior Dance group and also takes Pilates classes 2x/week, walks and walks with me.
We always take the stairs when on-board a ship (never the elevator), and don't have a problem getting in and out of tenders, onto docks or on board busses. In fact, we don't really like getting on the excursions where you're on a bus with a group of others. We much prefer to walk into town and do our own thing after researching the things to do in those towns.