The time between dock flood-up (which is what I assume MSOCS is alluding to) and sea trials will be spent in finishing the outfit of those decks above the hangar deck and setting to work the systems.
The "engines" have been in the ship for nearly three years, depending on whether you're talking about the diesels, the gas turbines or the electric motors. What is happening now is that the various systems are being pressure tested, flushed and slowly set to work, in the same way that the mission systems will be calibrated, trialled, debugged and adjusted.
The original question is a little bit like asking what the Typhoon will be doing between delivery of the first production cab to the OEU (2005)and the declaration of IOC (2008).
As for the "at most 12 aboard" - that rather depends on whether the light blue decides to play joint properly this time....