Chopper, people need to see the Law under discussion.
(l) Misconduct while the ball is out of play. A player, must not, while the ball is out of play, commit any misconduct, or obstruct or in any way interfere with an opponent.
Penalty: Penalty Kick
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If a penalty kick is awarded but the offending team is guilty of further misconduct before the kick is taken, the referee cautions or orders off the guilty player and advances the mark for the penalty kick 10 metres. This covers both the original offence and the misconduct.
I guess your question covers the advancement of the penalty rather than the issuing of the card. I would advance the mark to the 5m line per Law 21.2:
21.2 WHERE PENALTY AND FREE KICKS ARE TAKEN
(a) ... If the place for a penalty or free kick is within 5 metres of the opponents’ goal line, the mark for the kick is 5 metres from the goal line, opposite the place of infringement.
As to the issuing of the card, it's interesting that the ref is given no option in law - the card must be given. On that basis, when we march a side back 10m for throwing the ball away we would all indiscriminately issue yellow cards as well. Any takers for that black and white approach?