R's Rule for Distance Visits (i.e. driving 2 hours to see relatives) to or with Small Children: If anyone on either side of the visit, be it adult, child, visitor or visitee is feeling even mildly ill, DO NOT GO. Just take a rain check and do it later. If later is not possible, then the one non-sick adult who can travel may go if absolutely necessary, but leave kids out of it entirely.
Corollary: On days where the children just will not nap, it is best to punt any evening plans that include children. It would be less stressful for all involved to stay home, sit on the couch and order in pizza. Any disappointment that ensues on the part of any party pales in comparison to the massive headaches that will ensue should you try to go ahead anyway.