I agree about not driving the motorhome on Avenue of the Giants. I did it last year and a couple places were sketchy (very narrow). On the other hand, Newton Drury Scenic Parkway is a very pleasant redwood drive in the motorhome, which I highly recommend.
I love the Oregon Coast! Get the Mile-by-Mile Guide (online or in the mail). Lots of State Parks, commercial RV Parks, and a few Elks Lodge parks if you happen to be an Elks member. Some of my favorite sightseeing places are Hug Point, Yaquina Head Outstanding Natural Area, Cape Perpetua, Jerry's Jet Boats on the Rogue River at Gold Beach....just to get you started.