To see both Victoria and Vancouver without taking your RV I would suggest staying in Anacortes Wa.
From there you could take a day trip to Vancouver, about 90 miles, Fidalgo Bay RV Resort in Anacortes is very nice. While there you could take a day trip into the San Juan Islands. Whale watching is one option.
You can catch a ferry to Vancouver Island from Anacortes but would make for a very long day trip.
A better way would be to drive down and catch the Port Townsend Ferry with the RV. (I'd say around 90 bucks for RV and toad, reservations recommended.
You might want to spend a night in Port Townsend. Very neat town. Fort Worden State Park is fantastic. From there you could head to Port Angeles and take the ferry to Victoria. As previous poster stated, no car really required.
Be sure and drive up to Hurricaine Ridge while in Port Angeles.