As quick as you can, get all your children to take a whole bunch of Vitamin D. Even better, if you can strip them down to their shorts and have them out in the sun for about 15 minutes, it will probably help a LOT. Vitamin D fights flu in half a dozen ways.
Next, give them all Cold-Eeze lozenges to suck on, not chew, and nothing to drink for a half hour afterward. They will taste ucky, but they are FDA proven to shorten duration and intensity of colds, and likely the flu. They have a unique kind of zinc in them that inhibits the virus from reproducing.
Then if you can, get pure cranberry juice and start pouring bottles of it down your sick child. The pure stuff is very bitter, and they have to drink a lot of it, but it can strongly interfere with the virus attacking their cells. The more, the merrier. Typical sweetened cranberry juice is only 26%, so you need to get the pure stuff if you can.
Try cranberry capsules or chews, located in the vitamin section. One chew is equal to just under a gallon of juice. They taste pretty good too.