Thanks all for your replies - sorry I haven't replied sooner, I've only got limited internet access at the moment.
Thanks for the reassurance that I am on the right track with the explanations so far.
Katelyn's Mom, dd has been in child care and more recently preschool since she was 7 months old, so she has been in 'formal' settings most of her life. I guess one thing that leaves me wary is that she had an awful preschool experience last year, which I am not keen to repeat. She was friendless, the teacher seemingly didn't take to her and she was terribly bored by the activities (the result, extreme lethargy, not wanting to get out of bed for hours on the days before preschool etc). I suspect it has left me more wary than is useful. The advice I have received here and elsewhere to give it a chance first is advice I will take and see how we go.
The stories you've provided have given me food for thought, so thanks again!