Here's one I started earlier, but feel free to use the idea, it's based on actual events that happened to me earlier today.
A man and his two small children go to a fast food joint before going to the grocery store. Shortly after they get to the store and begin filling their cart, the man's stomach starts to churn. Knowing he can't use the toilet at the store with two small kids, it becomes a race against time to get his groceries and get home before messing his trousers.
Some potential problems that arise, one lane being open for 50 people trying to pay. Morbidly obese people in motorized carts blocking the aisles. Kids going crazy and getting in to everything. Woman flirting with the man as he tries to play off the rumbling in his stomach....