I'm very heartened by the numerous replies and encouragement to do some pushups.
A friend of mine is a personal trainer, I'll be seeing her next week and will ask her to show me how to do both push ups and sit ups (the former I really can't do while the later I end up moving in a walrus lurching style from one end of a hall or room to the other and look very dorky doing too)
I have a walking app to track my daily walking (usually a min 1½ - 2 miles (2 - 3Klm) per day) so push ups might become a thing I do, too. (Just as an aside, I got advised to "walk up all flights of stairs briskly" for a very short burst of exercise which I've been doing for close to twelve months now).
Adding push up to that list won't be very bad. You know push ups comes with it's own swag and uniqueness. You know someone people say that exercise is not complete without adding push ups and I think I kinda beginning to agree to that saying since I started this challenge.