Cultus Lake Park
Try Cultus Lake Park (http://www.cultuslake.bc.ca/) in the summer for a refreshing dip or stay in one of the lakefront campgrounds. Weekends tend to be overcrowded. About 10km south of Chilliwack.
Cultus Lake Waterpark
A fun summer attraction for kids and adults, and a nice way to pass a very hot day. Twilight rates are available, and while it's not the sort of place you need to go often, it's a good a one-day outing from much of the Lower Mainland, especially with kids. Best bets are late June and early July, or rainy days, as it can often be very busy.
St. Urban Winery tasting and tours
The vintner, who grew up in Czechoslovakia, works in the European style. Vineyard and winery tours available.
Hike! There are lots of nice trails in and around Chilliwack. A good place to start is the Chilliwack Lake Provincial Park (http://www.env.gov.bc.ca/...) where you can find several trails that are easy to get to by road and of varying lengths.
Fishing is popular on the Vedder River. Make sure you're in season and that if you need a license you obtain one. Licenses can usually be obtained at bait shops, and some other places too.