BC Ferries offers up to a 15% discount on one way fares when purchased as a Circle Pac ticket. This means you can go from the Lower Mainland to Vancouver Island, across to the Sunshine Coast and back down to Vancouver at a great price! Or go the other way around! The deal applies to autos and passengers, RV’s, and even motorcycles. Check with BC Ferries for the details, but basically you have 30 days to make your trip. Tickets can be purchased at any of the ferry terminals along the circle route: Tsawwassen, Horseshoe Bay, Langdale, Saltery Bay, Powell River, Comox, Swartz Bay, Departure Bay and Duke Point. Then keep the voucher handy for showing at the other terminals along the way.
It couldn’t be easier and you can go in whichever direction you like. A route I’ve enjoyed is from Horseshoe Bay to Langdale and then north along the Sunshine Coast through the communities of Gibsons, Roberts Creek, and Sechelt and via the Saltery Bay ferry on to Powell River on the Upper Sunshine Coast. The Sunshine Coast has fantastic scenery, great fishing, boating and hiking so stay overnight at a Sunshine Coast Bed & Breakfast to have enough time to get a real taste of this region.
From Powell River take the ferry across to the Comox Valley on Vancouver Island and an endless variety of both indoor and outdoor Vancouver Island attractions await you. You can visit rugged Cape Scott at the very north-western end of the Island, go whale watching in Telegraph Cove or on the west side in Tofino, play golf at any number of great Vancouver Island golf courses, visit museums or superb gardens. British Columbia is an outdoor person’s paradise, but it caters to couch potatoes too. Those who like driving trips can’t miss— much of the highway system is along the sea shore or through rolling hills and low mountains. Vistas are spectacular and you really don’t have to get out of the car to enjoy them, but you’ll want to, to experience the forests and seashore first hand. The ferries themselves are very comfortable and afford incredible views. You may even see whales from the ferry! I have. Everywhere along the way you will find British Columbia Bed & Breakfasts offering great hospitality and lots of local lore and information to enhance your journey even more.
Be sure to take in some of the many museums you’ll pass along the way. Not just those in the big cities where world class art, history and theatre are on display, but also those in smaller towns and cities where local history and aboriginal art and culture come together along with exhibits about BC logging and BC mining. 
There is a lot of fascinating information to be enjoyed.
Frankly, the only drawback I can think of around doing a BC Ferries circle tour of the Lower Mainland, Sunshine Coast and Vancouver Island is that 30 days just scratches the surface. Be warned, this territory is addictive! I’m hooked and I’ll bet you will be too. Have a terrific time, and then come back to explore your favorite areas in more detail on your next trip to BC!