I agree with the others. Sure it was an honest oversight, just give the Dad a call and let him know payment was due yesterday and you would greatly appreciate if he could drop it by at his earliest convenience. Chances are he will appoligize and bring it over asap, if it's not his normal routine to pay you, and Mom is clearly occupied right now with an awsome cruise, the last thing on her mind is to make sure you are paid. (although she should have remembered to remind him) I wouldn't give any late fees right now, just remind and ask for payment soon as you need to get to the grocery store for next weeks food!