its funny but this last winter when I decided to keep on riding in the winter to keep in shape, I started out with my winter boots and flat pedals. These were flat plastic type ones that had terrible grip, so I put some metal ones ones that were a lot better. I have to say though that after riding pretty much exclusively spd for the last 25 years, the feeling of not being attached in was very weird, and I didnt like it.
I didnt like it so much that I ended up ditching the boots, putting my spds back on and going all out with double wool socks and extra fleece material on top of my shoes before I put on my rain booties on my mtn spd shoes.
You've made your decision, but I have to say, I really dont like riding not clipped in anymore. I know it means usually having two pairs of shoes, but I guess part of it is just liking the really stiff soles of riding shoes.
Your tevas may be ok, and I guess it depends on how much you have to pedal hard, but my feet really dont like soft soled shoes anymore for riding, specifically my arches.
All that said, enjoy the short trip no matter what you wear. Where are you going if I may ask?