The Shedd lists Valentine's Day, this year, as a free day. :) So do several other museums... http://www.chicagohotblog.com/chicago-museum-free-days The Adler is free on the 15th, if you're still here, then.
I'd agree that the Field generally is fun, and though I would definitely not discourage the Adler, the Field has a classic meant-for-children museum feel. If you do go there, and not the Adler, you won't be much further from the lake, and it's easy, if walking is not a problem (I assume it isn't), to go from there to benches and paths beside the Shedd, where you can walk, or sit, weather permitting.
The Art Institute's got stuff on the lower floor meant to appeal to kids and families, and though I love the place, I am not sure the area meant for kids is as big or exciting an area as it could be. The Art Institute is wonderful, though, in general, and I imagine the brilliant color of the Impressionism collections being especially appealing to even quite young children. There's also the potential appeal of the Thorne Rooms' miniatures, which are wonderful... or (though I don't really like them), the glass paperweights on the same lower level.
Without knowing any details about this one, I think a Chinese New Year celebration sounds terrific.
Unfortunately, only now expecting my first children (2), I don't really have coffee shop recommendations for someone traveling with kids. I keep thinking of a place, and then realizing it's down the street from my in-laws, several states away.... ;) If you do find one, or someone else knows, I'll cherish the information!
Yay for carlessness and Amtrak! I do love them both....