I used 2 different childcare facilities for 2019. I have 3 dependents. Would I just divide what I paid between the 3 of them and then add the 2 amounts per child?

Yes, you will make a separate entry for each childcare facility so that you can provide their name, address, and tax ID number.  Then you can divide the amounts between your three children.  It may not divide out exactly equally since it's an odd number, and that's okay.