"quick-and-dirty" means: Done or constructed in a hasty, approximate, temporarily adequate manner, but not exact, fully formed, or reliable for a long period of time.... This is a fairly neutral word with no inherent risk attached. There is no real cause for parental concern; it is descriptive vocabulary rather than something dangerous. If your child uses it, context will usually make the meaning clear. A brief, curious question about where they heard it is generally enough to know whether to follow up.