You may want to look around for in-home daycares. My DD attended a "center" daycare and was extremely frustrated in the 1s and 2s class (things were better in the 3-5 class). My son goes to a small in-home daycare with children from 18 months to 4 and that was a great fit for him at 2. He was much happier in care than DD was at age 2 because of the more organic mix of ages; he was able to hang out and play with the older 3s and 4s. Of course, now that he is getting older himself this is becoming a concern again.
I don't have any experience with Montessori, but I have heard it CAN also work for these kids. A very play-based, freeform coop preschool could also be great.
