Young children can become dehydrated pretty fast so please keep then hydrated by having them take small sips. Sounds like either the flu or food poisoning. If it continues or their fever climbs too high( like over 103) then they need to be seen my a doctor. You should be seeing a difference in them by today if they have been sick all weekend. I know with food poisoning I was knocked out for 3 days and tired alot. Best of luck and I hope your girls feel better soon.
Paula
It sounds like gastro....Plenty of fluids and rest and they should be ok. If it continues for 3 days take them to see the Dr.