Take a hike Jim. Seriously.
https://www.nps.gov/caco/planyourvis...-to-trails.htm
I've gone to most of these. My favorite is the really cool Atlantic White Cedar Swamp Trail at Marconi in Wellfleet. I've recommended this to others and they really liked it. I think your boys would get a kick out of it. Going down into a swamp walking around on a boardwalk though the cedars. There's an educational aspect to these places as well if that makes a difference, and it's free. I don't think they charge beach parking here.