vancouver with 2 kids in july
I should also add that when you're on Granville Island you can walk West along the sea wall to Vanier Park where there are a number of museums suitable for children; not to mention the wide-open spaces to run. You could get a picnic lunch together as Sam Salmon suggests and head over there to the Pacific Space Center (Planitarium), Vancouver Maritime Museum or see a Shakespeare play during Bard on the Beach.
Granville Island rocks with kids! My boys like the waterpark and the model train museum which is small and little weird and under-rated. They also like putting their own lunch together at the market with bagels from Siegel's and honey garlic pepperoni from Oyama and their choice of fruit. The gelato at the coffee house around the corner from the waterfront theater (by the beached boat) is good. The burgers at Market grill are awesome, the sandwiches at La baguette are very good - I think they do a picnic box too.
Dim sum is always fun with kids if they like Chinese food and big busy places.
Jericho Sailing Club is a great recommendation, especially in the afternoon. If the boys are young, bring carrots to feed the bunnies that hang out under the boats (on the field not water...) and walk the warf to see the fishers. Pitchers of beer on the patio for parents and burgers or nachos for all.
Run around Robson Square by the Art Gallery go up and down the stair/ramps then eat mediocre sushi at Tsunami where it goes around on boats on a little river (4-year olds love this - parents tolerate). Otherwise eat on the Gallery's patio or have a street dog.
Can you provide some more detail on their preferences, foodwise? I notice that you are from the Bay Area...which is similar to Vancouver gastronomically (minus the Mexican food, and a few other ethnic cuisines, etc.). I have two young daughters 7 and 10 yrs and I'll list a few trips that I though were successful.
Granville Island (take the little Ferries over)
Kits Beach area - small restaurants around the area - of note is Octopus' Garden for sushi
The Asian Food Courts at Crystal Mall, and Aberdeen Center
The Punjabi Market Area
Jericho Sailing Club's beach - it has a concession stand that serves decent fries, etc.
Taking the tram at the ski hills over on the North Shore for the views of the city
Museum of Anthropology at UBC
The Vancouver Art Gallery
A no-destination trip on the Skytrain and Seabus.
Walking around Robson Street and Downtown
Science World (can be on the same trip as going to Granville Idalnd - it is accessible by the little GI ferries...you can see the construction of the Olympic Village from there)
Rent a power boat over at West Van and boot around
Rent a kayak at Granville Island or take lessons
Walk/Bike (rental) around the Seawall around Stanley Park
Walk around the "other Seawall" - on the Granville Island side