HI C.~
As a Mom of two who had her kids in daycare and now a children provider myself, I understand both sides of how you're feeling!! The best advice I have for you is to be 100% comfortable that your girls are in a loving and stimulation environment. There are great daycare and no so great daycares and I have experience with both.
Be sure that your provider is keeping the kids busy with outdoor play, large and small motor skill activities, creative play, various age appropriate art activities, opportunities for growth with social skills, reading, music, dancing and physical movement and that they are in a safe and clean environment.
As far as illness... you can expect them to be sick often if this is their first time in care This is their first dip int he germ pool and it's actually good for them to build their immunity this way and now. Otherwise you will deal with them being sick just as often when they enter preschool or kindergarten. Just be sure that you are practicing good hygiene and that your provider is too. They should have a schedule of how often they clean toys and surfaces and a policy around hand washing. For example, kids wash hands before eating and after playing outside. They wash hands with assistance and for a duration of singing the abc's. They use paper towels and not all of the kids use the same hand towel.
How fortunate for you and your kids that you were able to be home with them during those first critical years!! And as amazing of a Mom you are, as creative and energetic and wonderful, you are just one person!! Your kids can thrive in an environment where they can work on social and preschool readiness skill with their same aged peers or even kids older and younger. It's a wonderful opportunity for them to learn flexibility and diversity in a small environment,and to learn trust and direction from other adults. Daycare can be a great stepping stone to preschool and then preschool to kindergarten.
As hard as it is to leave them with someone else, they are at great ages to to this. Try to look at it as a building block for their independence and security that will help them later. Just make sure that you have them in the right place... you can get a lot of information from your kids by talking to them and really listening to them as they talk to you about their day.
Expect there to be days when they cry on the drop off, and know that as soon as they adjust, (which should be a relatively short amount of time) they will be off and playing and no longer crying as soon as you leave. Then when you come to pick them up they will cry because they don't want to come home. That's a really good sign that they are happy where they are and no reflection that they love you any less.
Best of luck~ it is so very hard. You're kids will be ok and so will you! Pleas message me if I can be any help to you!
Take care!