They want the spot . . . ?

[playfelt]

And if the next interview wants the space and pays the deposit then take it and don't feel guilty about the first family that had their chance but dilly dallied too long. Once everything is set with new family I would probably send first family an email saying thank you for your interest but the space is no longer available. No explanation or further discussion just a brief message.

If they come back to you upset remind them they were given the chance to return with the deposit. When you didn't hear from them you assumed they no longer wished the space.