Have chains and know how to put em on, most likely you'll need em at some point.
Yes I5 up to Portland and I84 to Tri cities and 395 into Spokane is your best bet.
One good thing is last year and now again this year the snow has been very light with temps in the higher range . But that can change fast around here. Your trip back I'd head south before going east.
Now having said all that, I haven't seen any RV's on the road for the last month and most all of our camp grounds are now closed. But there is a couple of parks right on I90 in Spokane and Spokane valley.
Good Luck and watch the weather reports.