Both players going over line at FT

[crazy voyager]

I had this situation an a girls game I called last week. Apperently neither team knows that players behind the arc may only cross after the boll hits the ring, not all players anyway.
Sometimes only one player (the one who doesn't know the rule) runs erly and then I simply called the violation. But then suddenly,one player from each team run over the line, shot doesn't count so I couldn't cancle the game and tell them and then resume. What would you do?