Greater Trip Question

Ok, so I've been working on my intelligence fighter who tanks with a shield. Sub-optimal maybe, but I'm finding some pretty cool ideas to go with it.

My current question regards Greater Trip and using a Hooked Boss which states: Hooked Boss: The struts on this reinforcing boss bear large, sturdy hooks, which can be used to snag an opponent’s clothing or armor, causing it to stumble. You can attempt trip combat maneuver checks with this shield. If the combat maneuver check is successful, the opponent does not fall prone, but is considered flat-footed until the beginning of its next turn.

So, would trip maneuvers with such a shield still provoke the attacks of opportunity from Greater Trip? And if so, would the attacks of opportunity be against a flat-footed opponent, or one who has not yet become flat-footed? Particularly relevant since, depending on initiative order, it's entirely possible that I move (using the trip) and then the opponent moves (regaining his footing, and without even having to provoke AoO from standing) without my teammates every benefiting.