I am not sure that pulling kids out of day care would be a reasonable approach, as once they are in school, you are back in the same boat. Your kindergartener could be bringing home contagion too. Religious handwashing is your friend. If it is any consolation, evryone with kids your age is fatigued. Your problem is the pile-on of your infections.
Hope the Vantin helps.
Seeing an immunologist makes sense. Also, is there an infectious disease specialist available in hour area? You can ask your ENT about it.
Jan