I agree that December may not be the best time to launch. We are launching our next wellness related teleseminar intensive on Nov. 8th (with weekly speakers) and are building in breaks for the holidays.
We did something similar several months ago and the breaks didn't seem to make a difference in our teleseminar attendance figures, as long as I gave our subscribers plenty of heads-up emails that we were not having our usual calls those weeks.
But, as I have so often (and at times so painfully) learned, you will never know for sure unless you test it!