Scottie, I just pulled up The Weather Channel for the 18 and 19th of Dec in MN and it is to be 5 below zero about that time in MN. That means it should be a little warmer in MO.
I would make sure to bring winter boots, gloves, headscarf, hat, and maybe even some of the face masks because of the very cold air. I always try to wear these at times when windy and really cold. I also use handerchiefs to cover my mouth between car and building often.
Also, dressing in layers works the best. I like the little strappy tops under my blouse or shirt to keep warm. Polyester slacks aren't are warm as blue jeans. I don't wear panty hose either and always wear socks inside my boots. Actually, after one has lived around the cold for awhile your body sort of acclimates to it. We have been warmer in the states than we were all those years ago but I have heard that some of this weather may come back. In the bad cold people don't go out without a darned good reason, work, doctor, get groceries. We also combine trips to save wear and tear on us and on our cars.
I am glad you get to see your son's family again. Seems like that baby was just born. Hope you have a safe trip and a great visit. Hugs, Irish