The state parks on the north coast will more than likely be full this weekend. While they are more money, the private parks might be your best bet. Premier Rv resort, logan road rv park, or Devils lake rv resort all in Lincoln City are all nice. Cape Kiwanda RV resort in Pacific City or the KOA in Warrenton also worth a try. One other we have stayed...Sea and Sand RV park outside Depoe Bay.
PS . Might try Devils lake first...I called Monday for a space this weekend with no problem getting in