J.R.
J.,
First and foremost, keep in mind that kids are extremely resilient. Also keep in mind that (unfortunately) divorce is much more common/accepted than it was when we were kids. Chances are good that they know plenty of other kids that are in similar situations.
Aside from that, I'll share some good advice that I received when I went through my own divorce:
1. Keep your kids sheltered from the details of the divorce.
2. Don't trash their dad in front of them.
3. Keep their routines as steady as possible.
4. Make sure you and your husband reassure them that you both love them, and the divorce is not their fault.
5. Start new, fun traditions for birthdays and holidays so they don't get sad about the way things used to be.
6. Stay positive. Laugh. Dance. Joke around. Kids are very intuitive, and they'll pickup your vibe.
7. If you choose to date, don't introduce anyone to your kids until you know for sure it's a long term thing.
8. Shower them with lots and lots of hugs and kisses!!!
I wish you lots of strength and patience as you go through this. Being a single mom isn't easy, but it's better than being in an unhappy marriage.