B.Z.
I read about an idea to make the first couple weeks easier, but I cannot recall the source. To ease kids with transitions, create your own book about the daily routine. It is best to have someone come along with you to take the pictures.
Here's what it would look like:
Take a picture of you and your daughter and son eating breakfast, take a picture getting into the car, take another at the daycare facility (or wherever she's going during your work hours), take a picture of her laughing there or doing something enjoyable, take a picture of you picking her up and hugging, etc.
It can be a small picture book that you can talk about together at bedtime, and she can take it with her, too.
I checked our son's book collection but didn't find any titles that jumped out at me to help with this change. Katy and the Big Snow (Burton) is a book that discusses how a female plow works in a town. Perhaps that would open up some discussion?
Good luck!