A small group of New York City children will arrive in Ridgefield this week as part of an initiative from the Fresh Air Fund. The children will spend a couple of weeks with volunteer host families in Ridgefield, Newtown, and Wilton. The Southwest Coast Connecticut Committee will be welcoming the children Friday. Volunteer host families share part of their summers with Fresh Air children, ages seven to 18, who leave behind the city streets to run barefoot in the grass or see the stars at night.