Every child is different, and so is every family, so I hesitate to offer actual advice. But I can share our experience: We tried a "toddler preschool" co-op when my daughter was 18 months, and realized within a few weeks that it was a terrible idea. She is highly sensitive and very intense, like many gifted children, and at that age, like most toddlers, she was not very good at managing those things. The chaos of the environment, with all the noisy, active toddlers and hundreds of toys was overstimulating. She held herself together while she was there, usually by getting intently absorbed in one toy and ignoring everything around her, but as soon as preschool was over and we left she would fall apart emotionally, with wild or defiant behavior, tears, tantrums, etc.
We then tried a Waldorf parent-tot program, which was a completely different story though ultimately also unsuccessful. It was held at the teacher's lovely home, and the environment was subdued and quiet, with only a few toys made of natural materials. It proved a terrible fit as well but for different reasons. My daughter has always been extremely physically precocious, and she has a very active mind to match her active body. She would quickly grow impatient with the slow pace and simple, low-key play being offered, and instead would go romping through the house, exploring the off-limits areas if I turned my back for a minute, such as the upstairs bedrooms, the basement, even outside. I became very self-conscious about my child being the outlier kid who wouldn't play "normally" and didn't really fit in.
However, it was a very different story a year later (age 2 1/2) when we enrolled at an emergent-curriculum, mixed-age preschool that emphasizes social-emotional development. That year was fantastic for my daughter. Even though she began the year somewhat still in the "parallel play" stage, she still learned so much there about emotions and relationships by watching the older children and through the excellent emotion coaching the teachers did. As her play became more interactive, she was equipped with a great foundation since she had internalized all that learning. At this point, I would call her social skills and emotional awareness very good for an almost-4-year-old, and I credit the preschool. I don't know that keeping her in one of the toddler-age programs would have made much difference in that regard.
Of course, our problem now is that she's no longer the youngest in the mixed-age class. Instead of learning social skills she's mostly having to learn patience (over and over) because there are so many younger children who are still learning. Patience is a good thing to learn, but I am beginning to question the value of expecting a child that age to have to practice patience for hours and hours every week instead of getting to be engaged and stimulated herself. (For example, instead of bringing things for show-and-share day that truly excite her, she self-edits, choosing items based on what she thinks the "little kids" are capable of handling without destroying.) And all of this is a separate issue from that of cognitive development/learning, which has become highly problematic for us this year.
Hope this helps, and good luck!
P.S. I third the suggestion not to cut, or even loosen, the cord yet. Building a secure foundation in your relationship with your baby and toddler, letting them lead the way toward independence, really pays off later, I can attest from firsthand experience!
