I've just encountered a situation playing this with my daughter where she has played the Finger of God and there's a Play All card in the table. Does this mean she can keep Playing Finger of God until there are no more Creepers on the table? Seems to be a loop.
Based on the wording of the card, and a strict interpretation of the rules, yes.
To be more specific, if the rule "Play All" is in effect and your daughter has played the "Finger of God", she may choose to smite a Creeper in play and, in doing so return the FoG to her hand, where she must, at some point in her turn, play it again.
At which point, she can again choose to smite a Creeper, and so on until either there are no Creepers left, or she chooses to not use the FoG's ability, or for some reason she is not able to play the card again (e.g. the rules change back to "Play 1", or she trades her hand with the FoG in it).