What would you have done?

Who's to say it didn't belong to the owners previous to this family. Maybe they know their inlaws could never have had that much money saved, and that is the reason for no contact. No one really knows where the money came from. And I would concider it as part of the purchase of the house , thinking the people that put it there loved their home and they wanted the new owners to invest it in fixing the house up.
Keep it use it to do some renovations and concider it a bonus. The children didn't deserve it or they would have gotten it before it was placed there. Do you think they gave a percentage to the previous owners of the house before their relatives bought it. "No",
I think this guy showed his kids how much of an idiot he really is. No thought went into his decission. He just assumed this money was theirs. Wander how he feels now ,maybe facing forclosure like most are in this economy. "Be a man put your kids in a shelter they'll learn from it".

I myself would heve kept it and threw one hell of a weekend party for the whole town, Live: Country and Rock. "No rap", all you can eat, drink and what ever. Just bring your Mopar to get in. Thats how I Roll , "PARTEEE" I wouldn't have had to think about it. And Screw the lesson for the Kids. You think they really care. Bring -um to the Festival they'll learn more life lessons right there.