A really healthy, physically satisfying but not too strenuous way to have fun is to go golfing for a morning or afternoon.
Go to a public golf course, rent some clubs, and walk around, and give it a shot. Hit some balls. Who cares if you're good at it? The idea is just to get out, walk, and do something different. You could take a one-on-one golf lesson from a resident pro or get your own group together for a fun outing.
Walking around 18 holes or so really gets the circulation going. (Don't hire a golf cart or caddie, OK?) The arm swings with the clubs are good for upper bodywork. Being outside also gives your lungs a lot of air and your body a lot of vitamins from the sun.
If you've never picked up a golf club you're probably thinking I'm nuts to suggest this. Maybe you always thought golf was something rich businessmen did--not for you. But there's a reason golf's so popular.