After much deliberation and research, in a frantic state of needing child-free time to get things done, I literally walked into the perfect daycare/preschool program.
Not only do they have an opening with no waiting list, they are willing to let DD crash the "advanced" toddler program one year early. We were there for an hour playing inside and out and DD loved it. Today she alternated between the teacher for 3.5-4 year olds and the teacher for 4-5 year olds. They encourage that.
So being in with kids younger than her and being in too rigid an environment were my two biggest concerns and voila! they are non issues. Yippee!
This was recommendation from my next door neighbor, whose college aged kids went there 20 years ago. It's the Parks and Rec child enrichment program in a low income neighborood. It's the same toddler teacher! Think of all her experience.
