There is a doctor in Rhinebeck who specializes in natural remedies- nutritional and dietary supplements. Dr. Rita Kirsch is her name, I believe.
Be aware, though, that ADHD is not a metabolic disorder, it is neurological. Changing a child's diet to be more balanced will often improve daily functioning and reduce "hyperactivity", but don't expect a quick change or a noticable increase in sustained attention.
I am not a proponent of inappropriately medicating young children, but stay in close contact with your children's teachers, school psychologist, and pediatrician to determine whether or not there are genuine changes as the holistic treatments for ADHD are not supported by long-term research.
Medications, when given correctly and closely monitored, can drastically improve a child's functioning, self-image, peer relationships and family dynamics. That being said any doctor who considers medications for a child under the age of 5 is poorly read on the topic.
Also keep in mind that diagnosing ADHD before the age of 8 is risky- children's neural pathways are still highly maleable until the age of 8 or 9. Try genuine behavior modification and consistent routines. If your children respond positively, then they probably do not have ADHD. Children who are geniunely diagnosed cannot inhibit their responses in any situation! Try the book "Ritalin is Not the Answer". I can't recall the name of the author, but there are great suggestions regarding behavior mods!
Best of luck-