During the summer Oregon State Parks really need reservations, especially on the coast. Mt Hood area. MtHood RV Village in Welches is the closest ful hookup park to the mountain.
Can I make some suggestions?
Coming into Oregon on I84 or thru WA on I90? If the latter, dont miss the Columbia River gorge east of Portland. You could park at Troutdale. If your coming in on I84, at Ontario take the highway west toward Bend, spend a few days in the high desert region of central Oregon. So much to see and do. Work your way north on 97. Columbia river, I5 north out of Portland, follow the signs at Longview,WA back across the river to US30 to Astoria to start your journey.
How much time are you alloting here? Could spend a month and not see it all.