I don’t even remember what keeps young kids occupied at that age. Does anyone remember trips when they were younger than kindergarten?
If someone didn’t live next to the sea, or get to a beach very often, getting a beach cottage with easy access to a part sandy part rocky walkable coastline is relaxing and kids can do kid things.
If you’ve never been there, Alaska will literally feel like a different country - very cool to visit, and kids can do kid things there as well. Taking the ferry is really cool if you’ve never done it, at least for the first few days - of course some kids travel better than others. Summer on the coast is chilly all summer - not shorts weather.
If you find an island to stay on anywhere in world, you’ll always remember it. The town will be different - everyone knows everyone and they know you’re new. It feels different, the locals are different, the experience is different.
I could easily sit on the beach at Tahoe every day for a month - summer weather is very comfortable. Some rentals come with local beach access and some don’t.
I could also sit at Grand Teton national park for a month and relax. Plenty of nice weather, any kind of local trip you might like, and good food at the lodge or in Jackson.
I could also sit on the beach for a month on the outer banks of NC. Weekends are ridiculously busy, but most of the population leaves during the week - it’s a little weird, but the food is also good.
Estes Park in Colorado is very comfortable in the summer - short hikes, nice drives, big mountains, good food.
Dude ranches in the Rocky Mountain states are stupid as sht, but you’re in a nice semi rustic place with nice weather, get to ride a horse, catch a fish, wear a cowboy hat, take it easy and enjoy being outdoors without being outdoors.
Out west there are rental cabins in the middle of nowhere with nothing to do, few places to go, too far away from towns to go in every day, and you’ll be forced to relax and be bored - like house sitting for a relative you’ve never met. Lol
Cody WY is nice - whatever you do it’s relaxing. It’s a chance to experience what most of the state used to be like. See some bears and buffalo at park if you want - maybe a wolf. Traffic in the park sucks.
There are also weirdos who simply get a bed and breakfast room for a month in a place they’ve never been and simply live like a local - do local things, like the locals do. Weird right?