Every school and every yard needs a swing set. I've posted plans for a swing set similar to one that I built for a day care center my wife and I ran out of our home in Texas. It's tough, creates a smaller footprint on the playground and allows you to play games like "Cut the Butter" without colliding into a support pole. It's all wood and can be built with basic carpentry tools (no welding). They make great garden swings too and will make your wife happy. Women like swings a lot for some reason. Something to do with romance, most likely.
"Me and Dad made this!"
At any rate, a nice swing in the backyard will win you some serious brownie points with the missus. Your kids will certainly enjoy them. They look nice and they show off your manly carpentry skills. This is a great father/son or mentoring project and the kids can really help with bolting things together, stirring up concrete in a wheelbarrow, digging and other stuff that may aggravate your arthritis. Also it gives the kid bragging rights for having help build the swings.