My wife and I are goingt to the Oregon Coast for the 4th of July.
Not to discourage you, but on the 4th of July? PCH 101 will be like a LA Freeway during rush hour...all day and night long. I read an article last year that it was rated the most congested highway in America on that holiday. I stay well away from the coast on Memorial Day, the 4th of July and Labor Day
Also, the 'haystack" rock at Cannon Beach is one of many "haystack" rocks on the Oregon coast. The largest is actually just offshore of Pacific City...
Tillamook is a nice place to pass through, but isn't a destination (other than the cheese factory & markets, which are a great stop). When the wind is just right, you will love the by-products of the cheese production process
But I am dwelling on some of the negatives here. The Oregon coast is beautiful and has many, many wonderful places to visit and spend some time at. You just might want to rethink when to do it. If you don't have reservations at this point, you may find it very difficult to get them for this year.