[sblock=Dr Simon]
Several points - I think Dj'hân's "Endure Exposure" incantation gives those touched immunity to his "breath" weapon, which as far as I recall includes Thorson and Edmond. Also without checking, Entangling Exhalation continues to deliver damage for another round, without reduction in damage.
The endure exposure effect that Dj'hân shared with the members of the group does indeed render them immune to his "breath weapon" effect.
Here's a description of the feat including the change that you requested. I'll add it to my character sheet so that you can reference it easily.
Entangling Exhalation
[BREATH]
You can use your breath weapon to create an entangling
mesh of energy.
Prerequisite: Dragonblood subtype, breath weapon.
Benefit: When you use your breath weapon, you
can choose to enmesh all creatures in its area instead of
producing its normal effect. Your breath weapon deals only
half its normal damage; however, any creature that fails its
save against your breath weapon becomes entangled and
takes an extra 1d6 damage, of the same energy type as
normally dealt by your breath weapon, each round at the
start of your turn. This effect lasts for 1d4 rounds.
If your breath weapon doesn't deal energy damage,
creatures damaged by the initial breath are still entangled
but don't take additional damage on later rounds.[/sblock]