You are a totally NORMAL and WONDERFUL mom.
We've all been there. Preschool teachers are VERY used to kids who are entering a structured environment for the first time. Lots of preschoolers have quirky speech patterns or speech difficulties, so again, they've been there, done that. That's what they do. And they are also used to being the surrogate mom, for those kids who do need more comforting, especially at the beginning. They expect it.
Your kids will be fine. May take a little adjusting, but kids are brilliantly adaptable, and in all probablity, they will really enjoy preschool.
I know I can't tell you not to worry, you wouldn't be a mom if you didn't. But take comfort in the fact that you are amongst good company with us other moms who have been where you are and survived! My son is starting his second year of preschool, and even though he will be attending a different school this year, I have almost no anxiety this year (notice I said 'almost'), in comparison to agonizing panic last year. For weeks, I didn't know if I could actually take him to his class and leave him there. But I did it. He was, and is fine, and loves preschool.