The Oregon coast is one of the most beautiful drives anywhere, and not to be missed. We go there every summer, attending kite festivals in Oregon and Washington.
If you are an Elk, there are several very nice places to stay with your trailer. If not, the Oregon State Parks are second to none, but make reservations, as they do fill up, especially on the weekends.
Towing, I would start at the north end of the state and travel south so that the ocean is on your right side. There are many places you will want to pull off for the spectacular views, and it is hard to do that with a trailer if you are traveling north. You can not make any real time along the oregon coast in the summer as there is much traffic and the road, for the most part, is one lane each way with passing lanes.
One good way to get to the northern part of the state other than I5, is to leave Creater Lake, and go north to Bend, over through the nice little town of Sisters, back through Redmond and north to the Columbia River near The Dalles. There is a very big one day quilt show in Sisters on Saturday, July 12th. Sisters Outdoor Quilt Show
The drive down the Columbia River Gorge from The Dalles to Portland is beautiful. Do some homework for this one. From Portland, over to the coast to Astoria, then south.
If you are interested at all in Kite Festivals, there is a nice one in Brookings Oregon July 19, 20. Southern Oregon Kite Festival
Harris State Beach, just north of Brookings, is up on a bluff, and very nice. Some spots have full hookup including cable. Again, reservations are best.
As far as Yosemite goes, it's like Rome. Everyone should see it, but not have to go there to do so. It's really beautiful, but not a pleasant place to visit. Crowds etc.