Was the paediatrician someone you've been seeing regularly? As an ex-teacher, have a word with your son's teachers and see what they think about it. Definately go with your instincts and get a second opinion before considering medication, especially if you don't see this doctor regularly - there are other options out there that are definately worth trying first IF you think that it is a problem (and it doesn't sound like you do) such as changes in diet, removing preservatives etc.
I do believe VERY strongly that there are children for whom medication is the best option, however I do not believe that it should be the first port of call, especially if you and other people who deal with your child on a regular basis do not see a need for it.
I have taught a child who had ADD but was extremely quiet and well behaved. The student was medicated but to me the medication did not seem to benefit their learning. The child had learning difficulties that made school more difficult for them in the first place and then also had problems with maintaining concentration which exacerbated their difficulties at school. In this particular case, I felt (and told the parents this) that the medication was dampening down the student's ability to actually participate in school/relate with their peers and me as their teacher which then meant that they struggled even more with their schoolwork. In fact the days that they didn't have their medication before coming to school were the days where I was able to get the most out of them academically!
Please, if you are in anyway uncertain, talk to his teachers and get their opinion, talk to a doctor you trust and who has had semi regular contact with your son etc. There are checklists that teachers/doctors will/should perform on children before even suggesting ADD/ADHD and these involve regular contact with the child not just observations in a 10 minute consult.
Sorry, this is one of my soap box issues smile. Like I said at the start, yes, medication is beneficial for some children but based on what you've said in your post I don't think it should be the first port of call so please don't feel pressured into going down that route straight away - get advice, do some research etc and make an INFORMED decision.