Just to throw in some of the standard suggestions with a little colour on top of the good suggestions so far...

If you're going to Richmond with a car, Steveston might be worth a trip. Kind of an old fishing village district thing going on with boats that sell seafood off the pier.
Granville Island is very standard. Parking is a pain in the rear on weekends. Lively, fun to walk around, and has a food market. Just off the island along a walkway is also a pier with boats selling seafood.

Walking across the Burrard Street Bridge to Vanier Park and Kits Beach might be nice depending on the weather. Or of course along the seawall area towards Stanley Park. Quite a number of areas to walk along the water actually.