C.C.
It's not in Scarsdale, but I've heard great things about the Rye Y summer program (http://www.ryeymca.org/camp.htm) and am planning on signing my 4 1/2 year old up for four weeks this summer. I've also heard great things about the Sheldrake Camp (a nature themed program) offered through the Mamaroneck rec department that your 5 year old could attend (www.townofmamaroneck.org). There's Camp Central for your 3 year old also in Mamaroneck, which my daughter attended last summer. She loved it.