Even though your family will benefit from getting fit doesn't mean you guys have to be the only ones to get something out of it. Lots of charities and foundations receive funding from the entry fees of walks, runs and bike rides that could give a whole further meaning to your fitness.
Plus, it usually takes some time to prepare for an event like this. This gives everyone in the family an excuse to get cruising around the neighborhood well in advance, encouraging each other to get ready for race day.
Want to go DIY? Consider planning an event for your whole block or neighborhood. Whether the races involve relays, potato sacks or three legs, it's a great way to get to know your neighbors while getting fit. As an added bonus: Have participants donate canned goods or money to local charities on behalf of the neighborhood!