Gosh...you'll be under the gun to get enough made for a sale now I'd think. Is it worth the "pressure" to get stuff made at this point. I believe most that do the holiday sales start up early in the summer so they have a good stash of items for sale.
This year, you might want to browse them so you have an idea of what is being offered and just chit chat them as to "gosh how long ago did you start making this...etc etc".
Don't want to be a bummer on your idea but also know it can put loads of stress on you at this super busy time of the year.