Consider Four Mile Creek State Park:
https://parks.ny.gov/parks/6/
You'll save a few bucks compared to private campgrounds and you'll be on Lake Ontario. It's just a short ride to Niagara Falls and also close to Youngstown or Lewiston if you're looking for a restaurant or grocery store and other shops. But make reservations as soon as possible, especially if you are planning to be there on a weekend. There is also a KOA in Lewiston which I'm pretty sure is less expensive than the one on Grand Island and in a much quieter location. And, again, 15-30 drive into the Falls depending on where you are going.
Our first RV camping took place at Four Mile Creek back in 1988 after we purchased a slightly used Starcraft Meteor pop-up camper. Our boys were 4 and 8, and it was a great Memorial Day weekend. We still have fond memories of that trip and the many family campouts and trips that followed. Bless you for taking in foster children and sharing your love with them! Have a great trip!
2012 Newmar Bay Star 3302
Blue Ox Avail
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2015 Malibu
"Get busy living, or get busy dying."
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