As MEA and MassEShep have nothing to do with each other, and AI is not a continuation of the Story, it is it's own play the Trilogy, take week off on Hello Kitty Online to simulate the 600 year cryo hibernation and go for Andromeda.
Again MEShep is not MEA. Same universe, different setting.
But If you feel the need to put it between ME2 and ME3, well too each his own.
But literally, we should play ME1, start ME2 until Character creation and hold it here, start MEA if there is some intro Content before 2185, switch back to ME2 and finish it except Arrival DLC, sworch back to MEA and play up to the point of leaving the Milky Way, switch back for Arrival DLC and finish ME3. After that, drink some coffee and finish MEA.
This way you totally stick to the timeline.
Might work on PC but i doubt on other platforms though.