I'll check how did these two do in the past when they played together.
Right now i only remember an amazing Trez assist and Iaquinta finish against Chelsea in Turin, but IIRC on that match we played with 3 strikers (or was it a 4-3-1-2 with Del Piero as a trequartista?).
The problem with Trez-Iaquinta, as Vlatko and few more noticed, is that Iaquinta always goes for a goal and he can only see the goal in front of him, never the other Juve players around him. Trez on the other hand, is a player who needs service.
A good match by Diego will nullify the problem, though.
A lot depends on Del Piero's fitness. If Ale is ready to play 90 minutes then Ciro has one more option, apart from Trez-Iaquinta, and that is Del Piero-Iaquinta (I'm not counting on Amauri as a starter for this match).
In any case, Iaquinta is the only one who must play. He's in better form than anyone else in our attacking department, he opens up smartly, runs more than the other strikers, he's making them tired, and, of course, scores and assists on every single match he plays.