As I pull my minivan into the farthest spot from the front door in the fully packed parking lot of the Walmart Superstore, my mood begins to slip in a southerly direction at an alarming rate. Weekly grocery shopping is not one of my favorite Nanny duties on a good day, but add torrential downpour, two cranky children with drippy noses and attitudes to match, and the task can slide from tolerable to excruciating in no time flat.