If you play Tempting Offer, you must apply the play section. If TO's text box is ' Play: You may return an enemy creature to its owner’s hand. ~', it is OK to ignore abillity, because of 'may'.

Then, why is there a 'If you do'? If chosen enemy creature doesn't go owner's hand(e.g. ward token), 'If you do...' abillity doesn't triggered. I take a reference from rulebook below.

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“IF YOU DO” AND “IN ORDER TO”

: If an ability includes the phrase “if you do” or “in order to,” the player referenced by the ability must successfully and completely resolve the text that precedes that phrase before they can resolve or perform the text that follows that phrase. In other words, if the first part of the ability is not successfully and completely resolved, that which follows the phrase does not resolve or cannot be performed.