Kids are the worst when it comes to Peten's effect because they basically read the effect (and thats all you should have to do *sigh*) and do what it says. The good part is, AT LEAST THEY READ IT! The bad part is, because of the hidden rules that used to only belong to we Judges, they are incorrect.
Peten can only resolve his effect if there is no other action involved when he is sent to the Graveyard. Archfiend of Gilfer is the same.