Cold weather and long car rides

In January I am leaving for the Texas/Mexico border for a mission trip we do every year. It is almost always cold there and we travel almost every day for anywhere from 3-6 hours. Last year was my first year being sick and I was heavily medicated with Norco and it was when I first started cymbalta. This year I am in much better condition but the cold always gets me and the long rides usually lock up my body pretty bad. I am looking for a few tips.

- I need recommendations for good warm socks that aren't super expensive and ok to wear with regular converse shoes.
- good pair of thermals and/or knee earners
- tips for dealing with the long rides

My feet and knees seem to be the most sensitive to cold, I also plan on getting a warm beanie as well.

The whole trip I also have to manage my gluten allergy which I am pretty much expecting to react from something as we aren't in full control of our meals every time we eat. So I am probably going to be bringing a small supply of pain Meds just in case anyway but I really want to do my best that I can otherwise.

I have wool socks I wear everywhere in coldweather. I rinse them out every couple of days. They are pretty fast drying.

As far as cars go, stretch as much as you can. I tend to drive straight through, but some people stop and move every hour or so.

Last night to a luminary exhibit at a battlefield. My hands and arms hurt so badly by the end just from the vibrations of the steering wheel. It was beautiful though--had some instrumental holiday music and the beauty of the luminaries,