It seems to be that I didn't have food poisoning after all.
Just as I was going to bed at midnight, E1 started complaining of a stomachache. (I was concerned since none of the kids ate much at dinner). Shortly after, E3 awoke to a puddle of puke. My night consisted of taking care of those two and doing a ton of laundry.
Somehow, (knocking on wood here) E2 seems to be fine after a bit of an upset stomach at dinner.
They all seem to be on the mend, and I recovered just in time. Grandma is sick now too, and sleeping. Hopefully we will be good as new for the weekend.
I spoke to the mother of E1's best friend at school, seems that she had it on Wednesday... going around.
Time to put in another load of laundry...