There's lots to do in Vancouver.
Stanley Park for sure; there's a zoo and aquarium well worth seeing, lots of park area, picnic spot, beach and walkways. Great family fun.
They also have these HUGE interior game places where you can video race against 10 at a time, do a virtual fight, fly a virtual hang glider, etc. Lots of fun. I dont know the name though, my cuzzin takes us there all the time. I think its called Playdome?
Great museums and art galleries; Some fancy car shops and China Town is worth spending a day at.... lots of neat stuff to do there for a day.
There's some good theatres too from the huge modern style to the classics. They also have a really good space, science center. Some locals can tell you about some of the hiking in and around? One good family place is
"Capilano Suspension Bridge" (Link)
Tourist site has most of the info:
LINK HERE or
LINK
I'm sure there's lots of other things to do too.
If you cross post to the Canadian Board, we have a number of active locals from Vancouver posting there too.
Enjoy!