D.B.
Kids don't get sick from being outside. They get sick from being inside with other sick kids! Other than being so cold that they get frostbite, what could possibly happen if they are outside in the fresh air? If they are feverish, you don't want to over-bundle them, but as long as it's not so bitter cold that their coughing gets aggravated, there's absolutely nothing wrong or negative about them being outside!! Go out and enjoy!!