One thing our pediatrician told us was that dissimilar pain medication (infant Tylenol and infant Motrin) may be each be taken at the same time, at full dosage, because they work differently. This was for cases of more severe pain - bad teething, etc.

Another thought on rehydration - Pedialyte's good stuff, but whenever I popped open a 1-liter bottle of it, my kids have either drank about several teaspoonfuls or none of it. Seems a shame to toss the rest. I found another brand called ReVital that makes a a similar product, but packaged in "Blue's Clues" squeezers - smaller bottles with a flexible straw that toddlers can hold and drink themselves, or it can be put into bottles for smaller infants. Comes in a variety pack of flavors (or, colors) and the kids can pick what they want, and be enthralled by Blue's Clues characters on the side of the bottle if they're so inclined. These smaller bottles might stash a bit easier, too.
Dave