I agree with everything CH said; she's definitely not wrong about child care providers being unappreciated and underpaid.
As far as your question, "Should I stay?"... I would say, "Only if you want to and only if you're doing it because it makes you happy - not out of a sense of guilt." The fact that they can't find a replacement and may have to close the infant room is not your problem or your responsibility. If you want to stay and a raise in pay would help you feel better about it, maybe now's the time to ask for more money.
Otherwise, you have the right to walk away from a job that makes you unhappy and not feel guilty about it.