My DD also starts kindy on 1st Feb, she is really looking forward to it- I am excited for her, and think she will do really well. Although I know where you are coming from about worrying whether they will fit in, be happy, make friends. I think the thing that makes me sad is that I am not going to be the one to take her for her first day of school, because am also a teacher and even though I work part time Monday is a work day for me and I have not a hope of getting the first day of term off , so her dad is taking her instead.
I does feel young though doesnt it, my DD's birthday is 23rd June, so she only make the cut off here in WA by 7 days, but I think I would be tearing my hair out if she had to wait that extra year

Can I just say though (talking with my teacher hat on here) the best thing you can do for her is continue to tell her how great Kindy will be, how much fun she will have, tell her how lovely her teacher is going to be, and on the first day, be brave and confident for her, walk in with a smile on your face, get her settled and try not to hang around too long- her seeing you linger and worry is only going to rub off on her. And if you need to have a good cry (which so many mums do when their first born starts school) wait till she can't see you. Even if she is upset, try and leave it too her teachers and teachers assistants, they are really really good at what they do, and they will call you if she gets really inconsolable. Usually though, there are so many fun, exciting and intersting activities for them on the first day, after the first few moments of worry, they are so busy and distracted they dont have time to be upset.

Good luck, I will be thinking of you Feb 1 as I am introducing myself to my own class, and thinking about my DD on her first day of school.