A ParentMap travel story highlighting kid-friendly lodges is full of great getaway ideas. A perennially popular one is Lake Quinault Lodge on the Olympic Peninsula. A few highlighted destinations, such as Lake Crescent Lodge, are closed for winter, but you could plan ahead for spring.
This article also contains a few ideas in Canada (on the last page), and travel to Canada is back open! Though keep in mind that crossing the border does require a little extra research and planning to comply with current regulations.