Ever since our son had a febrile siezure a few weeks back (I wrote about it here) the advice from the pediatrician has been to alternate Tylenol and ibuprofen as soon as he runs a fever. Apparently they have two totally different mechanisms of action, so you can really load a kid up on anti-fever meds without worry of overdose.

I'm not comfortable with doing this for more than a day or so, but it's better than another run to the ER with a siezing kid. . .

YMMV, and no, I am not a doctor, and I have not examined you or your kids, so don't take what I write about this and go and treat your kids without checking with your docs first.