Lots of options. From Vancouver, I like Alta Lake in Whistler because it is a catch and release lake with plenty of rainbow trout and some big cutthroat trout. The boat launch is also quiet most of the time so you don't have to stress about loading and unloading your car topper. It should still be ok right now for fishing later in the afternoon. The wind from the South can get pretty strong later in the day so watch for that if you are heading to the North end where the good fishing usually is.
Hicks Lake at Sasquatch Provincial Park is another good option, but it can get congested with the school holiday coming up since you're also there with the camping crowd. Lots of rainbows, the odd cutthroat trout and kokanee.
Kawkawa Lake is good for kokanee fishing right now, but again the boat launch can get busy especially on weekends since you're also there with the water skiining crowd. The 12 footer should be ok in the waves created by the ski boats but can be a bumpy trip.
A little closer to town, Buntzen Lake is another good one but I find the fishing really unpredictable. The boat launch is wide so plenty of room to take your time without interfering with others.
Cultus Lake has no shortage of fish, just mostly northern pikeminnow and other minnow species. There are some cutthroat trout, kokanee and landlocked coho salmon mixed in there, but it's getting pretty warm now so catching them is rare. Lots of ski boats on weekends, so time your outing wisely if you are going there.