Hi Kelly: I live in Vancouver and know my way around this area. You're going to need a map! That's my first suggestion - go to AAA and they'll give you a free map of British Columbia if you're a member, or charge you $3 if you're not. Or check Mapquest on the net.
Victoria is on Vancouver Island. No where near the City of Vancouver which is on the Mainland. You get to Victoria by ferry (No bridge - it's over 20 miles by water). Before you get to Seattle you have the choice of going first to Victoria and then to Vancouver or the other way around. Either way it's a circle route with two ferries. Take the I-5 all the way to Olympia WA then turn left and go up the Olympic Peninsula one hour to Port Angeles WA to catch the ferry to Victoria BC - it's about an hour ferry ride. You'll love the city, very British - stay at least a couple of days. My suggestion - stay at Abigails Hotel in Victoria. When you leave Victoria you drive north on the Island about half an hour to catch the ferry to Vancouver, it's about an hour and a half ride. Check the ferry schedules at www.bcferries.ca (they're every couple of hours usually). The ferries go between the Gulf Islands and the scenery is great. Stay several days in Vancouver. Go up to Whistler for a couple of days if you get a chance. (two hours north of Vancouver).
Seattle is two hours due south of Vancouver. You can find your way home from there!
Enjoy your visit and don't be afraid to ask anyone for directions or advise. Canadians tend to be friendly and helpful!