Best of luck!
We don't start until 9/2, but we have already had to purchase our syllabus and prepare for a math test the first day, as well as read several chapters in one of our texts. I'd wager they start you off with a bang!
Your kids may be teary at your departure. I'd get there early and tell them you're leaving, get your kisses goodbye, but maybe stay just a bit until they seem absorbed in play, then slip out. That way you haven't really snuck out--you've said your goodbyes for the day and they know you're leaving, but you give them a moment to readjust before you actually disappear.
Reassure them that you are coming back, with some kind of a time frame they can relate to, like just before dinner or after naptime. It's hard for really little kids to understand that your leaving is just temporary, especially if they're used to being with you virtually all of the time.
If you get major tears at departure, leave them in the daycare provider/teacher's arms. They really do deal with this often, and know how to reassure, distract, and resettle upset kiddos.
Sometimes, kids "punish" you when you return to pick them up. They may not come to you, or may not want to give you a hug--try to let it roll off your back and not take it personally. They may also be more clingy or more antsy once you get home--just reassure them, and things usually settle down in a week or two.
Here's hoping yours run excitedly into daycare, yelling "Bye, mom!," and run laughing into your arms, with big stories of how they spent their day, when you come to pick them up!
You'll all adjust! Just give it a little time!