D&D 5E (2014) way of mercy, way of long death or way of kensei for up to 6th level

[ECMO3]

I am playing an elf Monk, currently level 2 who will likely multiclass to wizard (bladesinger or warmage). I am not sure when I am going to multiclass but I am only going to go to 5th or 6th level in Monk. The campaign will end between 12-15 level. I am debating which of these subclasses to pick at the next level up.

This is the first time I have actually played a Monk. I am leaning towards mercy, partially because of the free skills.

Stats are: S7 D17 C11 I16 W15 CH10 (rolled stats)