I think your recommendation of the old port towns is spot on for someone coming from the mountain west. I love hiking in northern New England myself, and it is beautiful in its own way. But coming from Idaho OP will have had access to some of the most incredible mountain ranges in the world.

The old, historic port towns will be a completely new experience for them. The western part of the US simply does not have much in the way of truly historic, walkable settlements like that. Plus the ocean will be a totally new experience for someone from Nevada and Idaho.