I plan to run the led at 2.5v only and 200mA.
You do not have any choice at what voltage you run an LED at. It all depends on the materiel is is made from. For a power LED like this you need a constant current supply. You can set this to 200mA if you want.
So first of all you need to know what the Vf ( forward voltage ) of your LED is to see if 3V is enough even to start it glowing.
Anyway do you mean 3V or 3.3V which is more normal.