I guess it would depend on why you were taking them.
If it's just for a cleaning and you want to try and find someone you intend to see every year that specializes in children then I would sugest heading over to the tribal board and asking some local moms who they like and why. I would express your intrest in finding someone who doesn't push fluoride. Personally I would want someone who was holistic with an actual reputation for being truely holistic. By that I mean someone who looks at the whole child, thinks about nutritional aspects and tries to use the healthiest treatments, not just the cheapest/easiest for him.
If you're going because there are concerns already I personally would hope to find someone who also does ozone since it is totally painless treatment for cavities that works wonderfully. I would also want someone you does other fillings besides silver/mercury fillings.