tomminny,
When my kids (who have not been diagnosed with ADD -- I have) would go to their dad's for weekends and other visits, he saw the same thing and heard the same things from me as do you.
It was explained that the kids felt "free" to act out with me, but not with him. Most likely this was because they were on visitor-mode, but I am not going to speculate beyond that.
However, when I moved four hours away (for employment), their visits became more extended and less frequent with their dad (e.g., 6 weeks in the summer and rarely a weekend, as compared with 2 weeks in the summer and about a weekend each month).
After a couple of weeks at Dad's, they would start to come out of their well-behaved-visitor mode and act out.
As someone who is not happy being on meds because of side effects, and, quite frankly, lack of positive effects, I empathize with your concerns.
But I am still trying the medications because I have been this way all of my life, and it has been very difficult, especially socially. When I was a little kid, people laughed at the odd things I would blurt out. (I'm a female, so it is more obvious verbally than physically -- of course

) Later, in school, I was reprimanded for talking out of turn. As an adult, it is no longer cute, funny, or acceptable--especially when it takes the form of busily working on 10 things at once under the eye of a micro-managing boss, or inappropriately sharing irrelevent observations.
So, I guess you want to determine whether your son's behavior is just age-appropriate (if annoying to some), or something that is going to prevent him from achieving a tolerable life-style and acceptance.
There are people who have been able to channel their hyper-activity (both mental and physical) into extremely lucrative careers. For instance, although I read that Jim Carrey, the actor, is bipolar rather than ADD, his manic, ADD-like phase works for him.
But I suspect if the whole population of ADD folks could be counted, the few who have achieved great fame and fortune because they were not medicated would be similar in proportion to the number of basketball stars as compared to all low-income kids who think playing basketball instead of doing homework will put them on the fast track to success.
Sorry to ramble (as usual). I hope that gives you some useful ideas.