Essentially the skill-challenge aspect would be the background/in-game information gathered, etc. When it comes to social skill-challenges.
So the players would actually recite the actual poetry and me as the Giant would as well.
But the players would also roll to determine some things.
-Recite a poem, then roll to see how well their character was able to perform it, (diplomacy)
-Insight see what the Giant thought of it (give hints, information or misinformation if done badly).
-Bluff would be done to give players time to come up with a new poem, or intimidate, etc.
So basically while it would be actually roleplayed and acted out in-game things that determine how much it actually helps is somewhat determined by the dice.