Does your son need to go to preschool? In other words, will you be working or otherwise unavailable to him during this time? If not, then the best thing for him would be to have one on one time with you, playing, learning, customizing what you do based on his particular needs for that particular day. If you feel you have no option, in that you *must* work, then I wouldn't rule out the second one. Children learn very well in an age integrated environment. The age segregation thing is not good for children, really. It is a Marxist, humanist invention. Think about families. You have all ages working together. It's when you get the age segregated thing as the norm for families that you have families splintering. Older siblings with no patience or time for their younger siblings in favor of time with their peers. This is not a good thing! But, when you integrate the ages, way more learning happens. The olders learn patience and love for the younger, weaker in our society. They learn more by helping the youngers learn (you really learn something when you teach someone else!). The youngers learn to love and respect the kids a bit older than them, and they are encouraged to look up to the older kids. All around, everyone benefits! We are so programmed to think that the age segregated thing is the norm. It is not!! Well, it is now, but it is not the best way to learn or live.