For kids, during the ski season, the mountain has daily and nightly activities. Kelowna itself is a rather nice town, and can be a lot of fun. It is an artsy community, with an Art Center, an Art Walk, and more. Kelowna is also the Napa Valley of BC, with world-class golfing and hundreds of vineyards. Wine tasting is pretty much year-round. Kelowna also has a casino (not bad, but no craps table).
During warmer weather, Lake Okanagan is a lot of fun. The lake is 135 km long, and between 4-5 km wide. There are parks along the shores, and plenty of swimming, boating, and fishing (including rainbow trout and kokanee). It is said, by some, to also be home to its own sea monster: a giant serpent-like creature named Ogopogo.