12 vs.17 not that bigga difference. 'Course I am a low and slow smoker to start with. But if you had it all figured out for a 12, its just s little longer for a 17.
Just take your time, don't rush it, enjoy it while you are smoking. Stay with your plan, deviation is what usually causes the most problems. Personal I would be shooting for a 3 to 4 hour window for finished product prior to meal time. Resting the bird is good and safe when on the clock.
Patience Patience Patience
It will be ok...... If not you'll still have a holiday the family will always remember (and not let you forget)...... J/K
You'll be fine.