Hi KatieMama!  What an interesting school you describe-- I bet your son is enjoying the age-mixing on the playground.  My DD3 is also very social and loves playing with the older kids in the yard at her preschool.  
CCN-- I would love to hear more about your children's experiences in a bilingual school!  My DD is bilingual (Spanish/English) and will be moving to a bilingual (Spanish/English) preschool/elementary school in the fall.  It's been one of my pet theories that having to do everything in two languages keeps her mentally busier (and therefore happier)! I have nothing to back this up, just a theory-- but she does enjoy her two languages a lot.