I would be tempted to avoid December/early Jan for the Christmas reason alone, however IF our TTC goes ahead this year, and we fall pg straight away, then that is when I will be due... I dont think its enough of a reason to put TTC off. For us now its more important to try not to let the age gap between #1 and #2 get too big!
I cant think of any other months I would avoid... we have a good spread of birthdays throughout the year in our families, so it doesnt bother me.
Ideally I would also like to avoid the heat of summer with being heavily pg, but again, I dont think I will have the luxury to choose that next time around.