Science world for the kids, and, the planetarium and there is a miniature train museum at Granville Island and a boat museum not far from the Planetarium in Kits. There is the Museum of Anthropology at UBC, and, the Aquatic Centre in Stanley Park.
Kids like to eat at the Spaghetti factory in Gastown (as a grown up I find it not so good anymore!) or go up the Harbour Centre glass elevator and eat in the revolving restaurant.
Just a couple streets up from Gastown, along Cordova and Hastings are some cool shops like a shop of just umbrellas and a cool record store my teenage daughter loved, and, some really funky vintage clothing stores.
If the weather ever gets warm enough sit at English bay and watch the babes, male and female, all gorgeous, and there is great food nearby.
There is a tourist bus, a big red one, that stops in front of the Pan Pacific Hotel and it gives a great tour of downtown Vancouver. That will get you around so you know where everything is.
At Sinclair Center, (just up from the old CPR station which is now the sky train, sea bus, west coast express station,) there is a perfume store which stocks perfume from very small ataliers across N. America and Europe....very nice and not as expensive as you might think!!
Someone mentioned Grouse mountain tram, a definite must see, and, they have events up there in the summer. You can ride the chair lift down the mountain and back around again. If you have teenage girls you can listen to them scream at every swing and sway, the way teenage girls seem to do non stop.
Have fun