1) Disallow the goal and award a free-kick to the defending team. As far as I am aware, from an indirect freekick, the 'other touch' has to come from the attacking team and not from the defending team.
That is false Sean, the touch can come off any player be it attacking or defending. I've embarrassed myself playing in goal thinking I'd be clever and chest an indirect free kick casually, it hit a bobble in front of me clipped shoulder and went in.