There are plenty of natural-minded people in the Princeton/Plainsboro area. You might consider joining your local Holistic Moms chapter...? www.holisticmoms.org
There is a dutch language school up in Summit. If you're in Plainsboro it's not so bad because you can hop on the Turnpike and get up there easily but not quite as quick from Princeton.
There is German school (I think it's a Saturday morning culture and language program) in Warren. Also not particularly close but probably easier to get to from Princeton just because of the direction you have to go into.
Also, there's the Netherlands-America Association of the Delaware Valley out of the Philly area (so not far).
Last, Dutch history in NJ and the NYC area is ABUNDANT. I did genealogical research on many Dutch lines and they pre-date this country being a country. Everywhere you go (especially just North of Princeton on it's border in Belle Mead where there is a section called Harlingen; and then moving further North and slightly West into Somerset County) you will find place after place after place with Dutch names... Franklin township had tons of Dutch families as did Highland Park, Piscataway, Warren, etc. Old cemeteries with names like TenEyck, Vermeulen, DeGroot... the list goes on. It's wonderfully rich in Dutch history. There are old Dutch churches scattered around and much of the area bordering Princeton included old Dutch farms. Most of the libraries have information about this in their local history section. I am most familiar with the Somerset County stuff (that library is in Bridgewater--and easy shot up Route 206 from Princeton). Hopefully you will find it rich with history if not current-day Dutch culture.