I agree that one avenue is to strengthen the family's immune system. Look at your diet as the first line of defense. Focus on fresh fruits and veggies, whole grains, legumes (beans), nuts and seeds. Minimize animal protein and eliminate cows milk (www.strongbones.org). Use meat more like a condiment or a side-dish. I have lots of references to the power of food to help the immune system. I also have a list of immune supporting foods. Let me know if you'd like to know more. I also agree that you may need a little help in the nutrition category in order for your body to fight these infections more effectively. I work with Dr.s Bill and Jim (ABC The Doctors) and you might find some answers at their website, www.AskDrSears.com. We all recommend a food based supplement made from 17 different fruits and veggies. It has several independent studies that show a balancing and strengthening of the immune system.
The hardest thing right now is to get your house cleaned and eliminate the bacteria from it's hiding places. Depending on how you feel about that, you might enlist the help of professionals. Maybe have the kids stay with friends or family for a time so that you can keep them from reinfection.
I sure hope that some of this has helped. I know that a solicitation is the last thing you are looking for, but helping the immune system IS a strategy that would help your problem. I am happy to help, with or without discussion of 'products'. Good luck....I'm sure that you will get through this.
In health, D.
PS. Be sure you check on the independent research of any supplement that you look at. BTW, that supplement should have a nutrition facts label rather than supplement facts. That way you'll know you are getting food.