I can’t comment on the accuracy of the shipping date, but I have not heard anything about them being wildly incorrect lately.
As for making things by Christmas, yes it’s doable, but you have to get cracking on the learning curve. Read like crazy. Are you already pretty good at design and vector manipulation? That’s the part that takes the longest, really. If you get your brain charged up, you can hit the ground running.
Read literally everything you can stand. It’ll pay off.