Hmmm, part of my post is missing.
Breath weapons, if are natural for the creature, take the same percentage as a melee attack. If it's from a spell list, then the percentage for casting any spell.
For the drakes, their attacks can be combo attacks:
On Land: Breath + (1 claw or 1 bash)
Diving Attack: Breath + (1 Horn or 1 Claw or 1 Bash)
In this the breath attack still allows for a melee attack.