Hello,
Is it possible to put your son in the 3-day program, but with the class for children one year up?
Gifted children really stand out at this age so you usually don't have to deal with the headache of proving he is advanced. I have found that day care teachers are often less ridgid ragarding lock-step grouping.
Some gifted kids are happy with age mates. Your son has already told you that he is not. I would act based on his own remarks.