Scroll down for many suggestions for winter vacations organized in 9 regions, including choices for families with babies and tots, who have more freedom to travel during these months than those with school-age kids.
See also some ideas that cross many regions: Family Adventure Vacations are high-quality escorted small-group tours that typically offer a multi-sport experience in the Great Outdoors; winter vacation choices include Rocky Mountains, Yellowstone, Galapagos, and even Antarctica.

