My understanding is that a meio dragão não pode use the spell disfarçar-se to appear human. A half-dragon just has too many limbs for that to work properly, not to mention technically the dragon is no longer humanoid in type.
Type: Creature type changes to dragon. Do not recalculate hit dice, base attack bonus, or saving throws.
O disfarçar-se spell says, "You cannot change your creature type (although you can appear as another subtype)."
Pode o disfarçar-se spell allow a half-dragon to appear as another Medium dragon, a wyvaran, a drake, or anything similar to dragons?