Your situation is almost exactly the same as ours. Our DS4 has an Oct. birthday and had similar experiences with pre-k attempts. We decided against an early K start due to maturity issues and because we are aiming to attend a small K-3 school (24 students) that groups by ability (not age)....and they will accelerate kids beyond grade 3 material as needed.
We have gotten into a good groove with swim lessons, piano lessons, and a pottery class that was designed for older kids & adults.
If your son is into games like ours, we have found this to be a great opportunity for socialization. We found a math-game group that meets on occasion (huge success). He is now looking for kids on his own to play games with (not much luck with this yet).
