Family hikes/views/features

Hi, I'm driving to acadia from nyc this summer with my family. I would love to get some recommendations on things to do that are not super intensive so everyone can join along. The weakest link would do about 3 miles ish, nothing too crazy/steep/rugged. What are the best things to see? Also, in the most respectful way possible, what makes acadia a national park? What are the unique things about it? It seems beautiful but I'm wondering why it is a national park in comparison to other places that are not. Thank you in advance