Now now, I didn't say that Moka's father was the head of Fairy Tail...
It may seem likely but I doubt that Miyabi's 'boss' is Moka's father. She would have said, 'Father told me to kill anyone.' Whoever the 'boss' is, it is definitely not Daddy Starbucks.
I think that it is the Shuzen family who has connections to Fairy Tail moreso than dear ol' Dad. You've seen that the marriage between Mizore and Miyabi was purely a 'political' one. Why wouldn't Daddy Starbucks marrying the Shuzen woman be any less?