Hope this helps - it's perfectly natural for it to be hard to let go, but it's also good for you and for your little ones! I am only a mother of one, but I try NOT to make my son the center of our universe - it's easy to let that happen, but I don't feel that's what's best for him.
I had trouble taking him to MDO the first, second, and maybe a few more times, but I knew that he was going to be with wonderful people and eventually have a great time. Since he had never been to daycare, he was definitely used to being the center of attention and not having to share with anyone - be it sharing toys, sharing time and attention, etc. It was hard on him at first, but in a good way! Whenever he would cry, I would think "ok, of course he would RATHER stay with mommy or with his grandmother where he is doted on rather than have to learn to get along and play well with others. Does that make it right to let him call the shots? um, no." I also had utmost confidence that the ladies at MDO were fantastic with him. Plus, it was only for 2 days a week, 5 hours at a time. Even at 1-2, they are building their character, and I felt that it was good for him to socialize, learn, play, etc, etc...
So in summary, it will be hard...but it will be good for everyone in the long run. I think, especially for kids who aren't in daycare, that they are going to go through this at some point...and I decided I didn't want to deal with it on the first day of kindergarten! :)
Hope this info was helpful and not scary...good luck and God bless!