Are they for the wall or roof? Such a large exposure will probably require them to be 24" long which is expensive. Red cedar shakes will be shipped from the Pacific northwest and will be hand-split and that is more expensive than red cedar sawn shingles. The most practical and most common shingles in MA are white cedar sawn shingles factory dipped in stain or bleaching oil with a 5" exposure. The photo is of white cedar with a factory stain with a 4" exposure to match the clapboards on the main house.

30 lb building paper is what used to be called 15 lb building paper. I would avoid using the term "tar paper" because although it is illegal to use coal tar, some Chinese building papers have been found to have coal tar in them. Any specification should make it clear that any coal tar content is not acceptable. I would avoid the use of any kind of asphalt impregnated or coated paper if it isn't going to be supported by sheathing panels because it tears too easily and would require blocking at the horizontal joints. A high quality non-woven non-perforated house wrap like Tyvek or Typar would be better if the horizontal joints occurred over floor framing or blocking. DuPont Commercial Wrap would be an even better material since it is extremely difficult to tear. But I would add sheathing and a weather barrier or the Zip system from Huber. However a lot depends on the detailing of terminations at the windows, doors, soffits, etc. It is easier to get a uniform pale grey color with white cedar and white cedar is cheaper than red. For the beach I would consider the highest grade 15" white cedar factory dipped in Cabot's bleaching oil. I would use red if the shingles were going to left unfinished.

red cedar is generally considered more durable, since it has more tannins in it. Red cedar is red, not white, so you're a little more limited on the colors you can stain it to. White cedar is traditional in new england--think nantucket/cape cod--but red cedar isn't necessarily out of place. Overall, if you maintain either one properly, it should last for a really long time.

I love everything about it right now, except for the color of the shutters. I would much prefer them to be painted to match the roof. I dont think the house will look nearly as good painted white.