2 Answers

If you're pretty sure they're coming back to your home, after visiting someone, they should only take the clothes for that season. If they're permently leaving your home, they should take all their clothes for every season.

Having been a foster child for a year, I am sensitive to this question.  Think about it, they travel with their life belongings in a hefty trash bag...   Regardless of the circumstances, allow them to take what they want, all of their belongings, would be best, if that is what they want.  What good will their stuff be to you, as you will dispose of them after they leave.  Nice of you to be a foster parent, but do it for the kids not the money, too many do that!