I have a four year old and since he was two all he talks about is fishing, fishing, and more fishing. We go to the Fraser just up from mission bridge on the Abby side, the u catch place in mission, grace lake, and the Harrison. We live on lake Errock so there's always plenty of pikeminnow to catch at the end of the garden!
On the Fraser and grace lake we bottom fish with worms, he has caught coarse fish and trout from the Fraser and trout at grace. Just a light spinning rod works.
Next spring we will be going back a couple of times to the u catch in mission as he is really stating to get into fly fishing, he has a six foot 2/3 weight that he is practising his casting with at the moment. Hopefully by next spring he will be in the habit of keeping his sunglasses and hat on when fly fishing!
If it was my kids first time fishing I would definately head to one of the u catch type places, or the hatchery.
It really is great when they catch, there no snobbery over whether it's a pikeminnow, trout or anything else. To them it's a fish and it's cool! My two year old caught his first fish this summer off our dock and you couldn't get the smile of his face. Have fun