the only shelter that is needed would be a good windbreak. They do much better in the open air than in buildings. During the worst weather you would just need to bed them with goodly amounts of straw, corn stalks...
You say you have some woods, sounds like the perfect windbreak to me.............. depending on how thick it is and such.
You could put up a small Calving barn with individual pens for cold weather calving, or calve them in April/May and you don't have to worry about it. Personally I have had much better luck calving in Jan, Feb, and early March when the ground is frozen solid and not soft and muddy.
The only animals I have a conventional shelter available for is for the Herd Bulls............. and they only get access when the temp is going to be 10 degrees and below............ other wise they are all in open lots with windbreaks. My windbreaks consist of woods, tree lines, embankments, round bale stacks, and some man made devices.
Cows need excercise to promote easy trouble free calving. I feed at the end farthest away from the water source so that they have to walk back and forth. On the same tact, feed at night to promote day time calving.
Starting out you can go a little cheaper on the cows........... do not scrimp on your bulls....... they influence every calf that is born. Or, AI and you can pick the very best bulls and individually mate based on the improvements you want to make for each individual animal.
