We are Columbus schools, too. I can relate to being nervous about full day K, though I don’t have any experience with picking up early.
My son didn't go to preschool but was in full day home childcare with a couple other kids the same age. With our school, K started a week or two after the 1st – 5th graders had gone back. There were also staggered days so for the first week it wasn’t 5 days of 9-3:30. There was an adjustment period for DS and first day of K is tough anyways :-( Maybe even more for mom/dad, though, LOL!
He did great though. They had naps and 3 recesses - morning, lunch, afternoon. I feel my son’s teachers were really good at helping the kids adjust and I believe would have quickly informed us had there been a problem. Parents are encouraged to ask questions and we have always scheduled the Parent/Teacher conference so that we could talk to the teacher and get a stronger feel (than just his report card) for how he was doing. I also believe had there been a problem that they would have worked with us.
Definitely check with your school about their attendance rules. I saw one post about even being able to take them after attendance check – I think Columbus may be much stricter on this and her attendance would be affected.
Has she already had an evaluation with her teacher? If not, that would be a great time to ask about it too. Our school has parent consultants; you may want to see if yours does, too - very valuable source to answer questions, get info, etc. You could also ask about being a teacher's helper if your schedule allows; though she may also do better without you there. With our son I think he actually did better without us being there though I was able to get off work to go help with the Winter Party and Valentine's Party and I also went on the field trip to the zoo.
I hope this helps; please PM if you'd like more info.