Oh, it was in the Europe forum so naturally I assumed it was Maine, France. But beaches would be on ponds, lakes and rivers as Maine, France is inland.

There are lots of them in Maine. What part of Maine?

With small children, perhaps Dunes of Ogunquit but since we didn't swim, not sure about pool for young children. You would have to rent a second cottage to get a third bedroom. We've only stayed here once and we're not big fans of southern Maine but I really liked the large grassy area. Lots of play area and adults can sit outside and it's like one big yard.

Otherwise, I would look for an air b&b but might be hard finding one with a pool. Also keep in mind that some are located in areas where there is no WiFi or tv reception. But there's a long coast with a good variety of accomodations. You should find something. I'd recommend something with a screened porch.

There are tons of VRBO's that fit that bill. We've stayed a few summers in Maine in different places with our three kids. So we would have 3-4 bedrooms. Lots of good places on Coastal, Maine.

Check out Spruce Point Inn. They have lodging with multiple bedrooms / kitchen facilities and it is also a full - service resort. Quite lovely.

https://www.sprucepointinn.com/

(They do not have a sandy beach, but they check off everything else on your list).