A very hard question! Personally, I would make sure that the son with ADD gets treatment. It might not make a difference with his ADD - but it may also be the reason for his ADD.
The other son is hard though - I would have him treated, but with herbs only if possible. After having grown up with these infections, and knowing how much they can take from ones life - even as a child, I wouldn't want my child to go through that because I hesitated in treatment. It's only a 6 - 8 week treatment in the best case scenario.
I know that I will likely be in the minority with my opinion, but I think it's due to having been a child with these infections and knowing first hand how they can interfere.
I did find this article that might be helpful, it's titled "Neurological Manifestations of Lyme disease in Children" -
/sites.google.com/site/drjoneskids/symptoms-literature/neuro-manifestations