what type sail will be best for a two seater landyatch

A lot depends on the surface you are going to sail on and what is the normal sort of wind speeds you are expecting.
A 2 seater yacht needs power rather than speed to deal with the extra weight of that extra person.
So basically you will need a sail of perhaps 5 sqm or greater and with a fairly 'full draft' to give the power, a flatter sail gives speed rather than the power.
As I mentioned the surface, soft beach sand needs power where as a hard salt lake or similar is easier to get rolling on.