Welcome to Psych Central. I am sorry your son is suffering from ADHD. I did find natural remedy info as you requested here on Psych Central.
Psych Central - Search results for Natural treatments for ADHD

Besides being an active participant in helping oneself at Psych Cental, many people also help support each other by replying to other people's posts. Many people who are actively involved in Psych Central find it helps take them out of their own problems to develop empathy for others. And their problems are more manageable the more they help others.

Many people here at PC find they can share these feelings and what they are going through with the confidence that people go through similar things and can empathize. So many forums are offered as well as Chatrooms (after you have 5 posts or comments on others posts). Depression chat meets on Thursday night at 9pm EST and Anxiety Wednesday at 8PM.

You can also be an active member in other ways like supporting others in their questions, reading articles and posts http://forums.psychcentral.com that are applicable to your area of concern.

Please feel free to private message me or any of the Community Liaisons by left clicking on the name in blue to the left of their post) for questions or just to share.