stbmom -
please don't blame yourself or DH for following your child's lead in interests. If a kid enjoys an activity, and it's not harmful, then they are "old enough" no matter what the books say!
I don't know if your son percieves himself as a big kid, or just as a human, and wants to be doing what the "interesting" humans are doing. If the "interesting" humans just happen to be older, well.....that the child you got!
It sounds like you have intuitivly found ways to meet your child's needs. The whole point of "age related expectations" is that they work for many, but not all, people. It's so easy to forget this. But it's still true.
Here's a thought experiment that helps me hold my ground under critisicm:
What if school's were set up by height rather than by age? It would have certian advantages - sports,school pictures and assemblies, and some dissadvantages - but the dissadvantages would be the same as the current system, magnified for a few kids (gifted and short) and lessened for other kids (gifted and tall) The point is that the dissadvantages would be similar in kind - age, like height is a roughtly good, but far from perfect, guide to learning readiness!
I do think it's normal for gifted kids to go through some of same stages that NT (regular) kids go through at an earlier age. At age 9, "mental puberty" seemed to be setting in for my son. I couldn't believe it, yet, soon after the talk, came the smells and the peach fuzz. The physical changes are still subtle, but enough to assure me that I'm not loosing my mind. I think there is a kind of "mental puberty" that is quite independent of physical development, but just occurs when the worldview reachs a certian size and sophistication, usually blamed on changing hormones, perhaps wrongly.
((Hugs))
Trinity