If you didn't/don't like crossing the Hood River Bridge, then you would/will also hate to cross the Bridge of the Gods at Cascade Locks. They're both narrow and would make any Beaver owner pucker the whole mile. I am not sure, but the Bridge of the Gods may have a weight restriction that would preclude our coach weights anyways. The best places to cross would be either at The Dalles, Biggs or on I205 in Portland. The other problem you will run into is the tunnels up and down the Washington side of the Columbia River. I know there is a tunnel near Lyle, just downstream from The Dalles, and other tunnels downstream from there, but I don't remember exactly where the other downstream tunnels are relative to Bingen/While Salmon, Carson, Stevenson, North Bonneville, etc.
If it were me, then I would take 97/197 from Madras to The Dalles, and cross the river at The Dalles. Now realize 197 going down off the bluff into Maupin ain't no piece of cake, and crossing the couple hundred yard bridge at Maupin is a bit narrow too... but nothing like the narrowness and length when crossing the Columbia River at Hood River and Cascade Locks. Frankly, I don't know where Home Valley, WA is. But I would be looking for a better route to avoid the two narrow bridges and the tunnels.
Good luck... and may the force be with you.