Bellingham, WA on the US side is also served by Alaska ferry but that would be a much longer ferry ride.
In my opinion, visiting Alaska without seeing tidal wave glacier is like never been there. Most of the other sceneries in Alaska you can find similar sceneries just as nice in Western Washington and British Columbia. The only way to see tidal wave glacier in Alaska is from boats. Ferries often times will stop and get close to famous tidal glaciers (not sure about the SouthEastern AK ferries).
Be sure to ask your rental car company if the contract allow you to drive to Alaska and/or into Canada. You don't want to get caught violating contract (with a long drive, your chance is bigger). Rental cars do break down (mine did during my last trip to Anchorage-thank goodness I wasn't on a gravel road).
One more thing, southern Alaska panhandle is one of the rainiest areas (also the most beautiful area) in the world. That's just something you have to deal with visiting the area. Fairbanks is dry but there isn't much to see there.
If you do end up visiting the Alaska interior, don't expect to see Mt McKinley, which is only visible 20%-30% of the time, mostly in winter. I have only seen it once flying from Fairbanks. Plus, I don't believe Denali NP's shuttle is running in May, which means you have to drive on long gravel road, a violation of your rental car contract.