A.D.
I'd avoid places with snow unless you intend to just rent a cabin and stay put b/c it's hard to push a stroller in the snow. California (San Francisco, etc.) is always nice... I was on vacation in NYC in December and although a bit chilly it was a blast -- took my son then)... there are plenty of places to go and have a good time.... don't try to plan too much b/c they'll get over stimulated with all the new thigns to look at... I'd try www.vrbo.com to find a place to stay as well so that you can prepare meals/snacks/etc at your own pace rather than having to wait for a restaurant to serve you... esp when you're working around nap schedules...