Personally, I would go up 101 and stay at Harris Beach (Brookings), Beverly Beach (Newport) and Fort Stevens (Warrington). And yes, in May there will be rain so prepare for it...it will happen.
FWIW, most (if not all) of the pull-outs on the Oregon 101 coast highway are on the west side. When traveling north, it can be problematic pulling into the pull-outs and then getting back on the highway. Much better if you can start at Fort Stevens and then go south down to Beverly Beach and Harris Beach. You will have to either spend a couple of days going up or coming back down...so why not go up I5 and then cut over to the coast on Hwy 30 and start out at Ft Stevens?
We spend our summers (May thru Oct) at Newport. We have traveled most of the US and have found the Oregon coast our preferred area to stay and visit.
Have a great trip.
Ron