Most people would assume that Vancouver has always been the most important city in this region, however, Fort Langley was once the only European settlement on the banks of the Fraser River... well before Vancouver even existed!
Fort Langley National Historic Site is therefore an excellent place to spend a few hours, especially if you're interested in local history and even moreso with kids. Located on the south bank of the Fraser River, about 1 hour inland from the coast, Fort Langley is a restored Hudson Bay Company trading post. As a national historic site funded by Parks Canada, it offers guided narrations and many events throughout the year.
The bonus of visiting Fort Langley, the historic site, is that it's located in the village of Fort Langley. This is a cute village with shops, cafes and restaurants, all located in heritage buildings from the 1800's. It's a beautiful historic neighbourhood out where the rolling farmland meets the river. It's like taking a step back in time!
Fort Langley, about 45 minutes drive from Vancouver on the Trans Canada highway, is a historic town. The Fort itself (http://www.pc.gc.ca/lhn-nhs/bc/langley/default.asp) is restored and has period costume guides and the town of Langley has a few heritage buildings and a delightful main street for shopping.
In addition to the Fort (http://www.langleychamber.com/FF_attractions.html) There is the museum of Flight, (http://www.canadianflight.org) the Northern Railway museum, the Langley Centennial museum (www.langleymuseum.org) and nearby is the Greater Vancouver Zoo.
Have lunch in the Fresh Food cafe, part of Wendel's Bookstore, browse the antique stores and interesting shops including a 50's memorabilia store and a Christmas store. There's Gasoline Alley, a courtyard of shops and cafes. There are also a few wineries in the area that you can visit.