Hi, and welcome to Westchester County.
We live in Yonkers and I was raised in Mt. Vernon. I haven't found either community to be particularly crunchy, but have found some good resources nearby:
Chiro: Dr. Russell in Fleetwood. He and his wife share the practice. Very open-minded and excellent care.
Ped. We were seeing one in Eastchester. She was OK re: our not vaxing, but kind of ignorant about bf, which was a turnoff, so I wouldn't recommend.
Food Co-ops: Don't know of any in my immediate area, but we go to the farmers' markets in Greenwich, CT (not very far and you can get raw milk there!), at the New York Botanical Gardens (just a short hop to the Bronx), and at Muscoot Farm on Sundays (excellent eggs, pickled foods, and other things, plus critters to see).
As an AP mom to a nearly three-year-old son (ext. bf'ing and seriously considering homeschooling) I really wish I knew some like-minded mamas near me. Haven't come across any at the local playgrounds or pretty much anywhere else. Once met one at the Botanical Gardens, but she was from New England! If anyone around in Yonkers, Bronxville, Tuckahoe, New Ro, or Scarsdale would like to meet, count me in.
I don't know of any specifically organic restaurants (except for Blue Hill at Stone Barns, which is supposed to be great), but some of the non-organic places we like include A'Mangiare in Bronxville (Italian); Spice Village in Tuckahoe (Indian, great lunch buffet); Eastchester Fish Gourmet; and Ripe in Mt. Vernon (excellent Jamaican; the chef/owner beat Bobby Flay in a Throwdown!)
Oh, and for the poster looking for a good place to relocate in Westchester: Yonkers is a large and diverse city, also quite affordable in some areas, but the school system has been struggling for awhile; similar deal with Mt. Vernon (but it's a much smaller city). Bronxville and Scarsdale are very upscale and quite expensive. Hastings-on-Hudson and Dobbs Ferry are both lovely, but still kind of pricey. If I could afford to buy in Westchester, I'd probably choose the Fleetwood section of Mt. Vernon, Hastings, Dobbs Ferry, or Tuckahoe. Sleepy Hollow/Tarrytown are also really nice.
Good luck everyone!