Maybe you and your husband could switch off when the kids are sick. You could stay home one day, then he could stay home the next day and so on. If nothing else, this will let your employer know that you are truly trying to give your best to everyone and they should be a little more understanding.
That being said, kids in government schools tend to get sick a lot. It's just the way it is. The best thing you could do is to make sure they're getting a balanced diet and plenty of sleep (kids their age generally need between 9 and 10 hours per night).
Make sure that you are strengthening their immune systems in any way you can. Garlic is good. I put it in most of the things I cook and we're almost never sick, but my kids aren't in government school either, so not sure which is helping the most. Also always go for the antioxidant rich option. I use several spices that are very high in antioxidants, like currey powder, a LOT. Make sure that they are taking a comprehensive multivitamin every day and that they are brushing their teeth at least once a day (the mouth is the most common path to infection). Teach them about the importance of washing their hands several times a day, especially before they eat. Pink eye is caused by contact with fecal matter, so they are either not washing their hands after using the toilet or someone physically near them isn't. Either way, the best way to prevent it is to make sure they are washing their hands. Ask their teachers to remind them to wash before eating. Make sure that all of their meals include a starch, a fruit or vegetable and a protein. Berries have very high levels of vitamin C, especially strawberries, so they are very good for the immune system. In fact, pound for pound strawberries have many times the amount of vitamin C that oranges do. Pro-biotics will help strengthen the immune system too. And make sure they're staying well hydrated with sugar-free beverages, preferably plain, filtered water.
If you can get them to swallow pills, then when they are getting sick or all through cold and flu season have them take Vitamin C and Vitamin Zinc. This combination ALWAYS knocks out a cold before it can get it's teeth in me. As an adult, I take this combo twice a day when I feel a cold coming on. My symptoms don't get the chance to get worse and what I do have disappears within a few days.
Also, make sure that your food handling practices at home are sanitary. Often a "stomach bug" is nothing more than a mild case of food poisoning from improper food handling/storage at home.
Anyways, best of luck! I hope you can find some resolution or at least something that will make things a little better.