We stay at Ainsworth State park just eaast on Troutdale. A 30 min drive to the heart of the city but full hook ups and scenic area on the old road. They don't take reservations but if you get there before 2PM we have always gotten in.
2011 Silverado 1500 LTZ/Trail Lite 8230
Looks like (from your profile) you will be coming in from the east on I84. We were originally from the PDX area and moved up to the OlyPen. Go southbound on I205 from I84. When we visit grand kiddies our favorite RV park is in Oregon City, a Clackamas County Park called Clackamette at the confluence of the Clackamas River into the Willimette River, easy on off from I205. Reasonable rates ($20 a night) for power (30amp) & water hookups, no sewer but there is a dump station about half a blockaway that is easy to get in and out of. And the view is right on the river, very nice.