I didn't send my kids to preschool. I figured Kinder was soon enough. We spent that extra year together doing all sorts of things from adventures hiking and discovering leaves and animal tracks and trying to identify them to going to hands-on museums to story time at the library (hint - they don't care if your kid is WAY younger and in the wrong age group's story time as long as they aren't disruptive).

If he's there for the social interaction, can he bring things from home to do that interest him or does he have to do what they are doing?

It's so tough - the fit isn't there even when they're young, and it doesn't get better sometimes until they're a lot older.