Can I Crossdress My Way Out of This Arranged Marriage?

Our poor Half Elven protagonist had an arranged marriage sprung on him out of the blue by his mother. Not only did she effectively sell him for the dowry, but she's handed him over to marry one of the daughters of the orc she used to adventure with. At least our protagonist has thought up a last minute plan to get out of it.
They won't want him if he can convince them he's a girl, right?