OMG J., YES I FEEL YOUR PAIN! My son started kindergarten 2 weeks ago. Let me just say, it will get much easier. My first day was hard, but once he jumped off the bus with this big ol' smile on his face, and I realized he WOULD come back to me, I was ok.
I too cried in the morning when he got on the bus and it drove away with MY BABY on it! It was one of the hardest things I have EVER done! It took a lot for me to even let him ride the bus! I almost decided to take him, even though the bus would pick him up at the end of the driveway AND drop him back off there. Luckily I came to my senses and allowed him to ride...otherwise I would be driving there and back everyday, waiting in the looooong lines.
It was hard to not be there with him every step of the way. My mind was racing with all these possible scenarios of things that could go wrong for him. And I wouldn't be there!!! WHat if he gets lost, what if he encounters a bully, what if he can't get his lunchable open, what if????? I couldn't sleep the 2 days prior to the first day of school!
I think you MUST keep yourself busy today with other things. You can't think about it. Just focus on something else to get you till 3:00. I was soooo excited when he got off the bus! Then he told me how much fun he had and that made me feel a lot better. They will surprise you on how much they can actually do without you. He even knew his bus number by the time he got home from schooL! In fact, I asked him that morning if I could just keep him home with me forever. And his response was "No mommy, I have to grow up...I have to learn...then I have to move out...then I will come back and see you all the time!" LOL, kids amaze me!
She will be ok. Ask lots of questions when she gets home...be super excited for her, and it will help her be super excited about the beginning of her life!!! Keep those kleenex close by and hang in there!!!
(It's actually kinda nice now to only have my 3 yr old daughter at home with me. It is MUCH quieter around here, and outings are a lot easier! I still miss him though...)