He asked for a spell, not advice, was truthful and direct. And the best part of all, he had the common sense to post in the right area of the forum! I'm sure no one here can say they haven't casted a spell that wasn't exactly necessary. Staying home isn't harmful, but travel can be dangerous. I see far worse requests here. It's refreshing to see an innocent one.
However, I would like to say, you may want to consider asking them if a family member or adult friend of the family could stay with you at the house as a compromise. A dark empty house, after all, is a target for robbery, so it would be in their best interest for someone to watch the house while they are gone. I was a teenager once, I know how to sway the minds of cautious parents ;-)