Well I have been wearing some $35 on sale Bass pro knee high rubber boots with 1000 grams of thinsulate this year. Down below 20 degrees for all day, and my feet were fine. Not a great hiking boot, but I walk less than 1/4 mile, then sit in a ground blind or up in a tree. These boots have done fine so far, and would work well for what you are going to use them for. I typically wear one pair of normal socks and then some winter socks over that if its gonna be cold.

There are better boots for walking, and snow, but for what you want, I think 1000 grams of thinsulate, even in those rubber boots, will work fine.

--Jim