My son has always been happy to just do the regular class work, and if he never had anything difficult, he's be quite happy. All through elementary school, other than being accelerated a grade for math, he was quite happy. If we had asked him if he wanted to be accelerated for math, he would probably have said no - he is just not one of those kids that is thirsty for knowledge and needs more all of the time.
Having said that, at 11 he is in 6th grade in Middle School - he is now in a full time gifted program and in 8th grade accelerated math. Would he have chosen this for himself if asked ? Probably not. Is he thriving ? Absolutely. So - my answer - yes, you know better.