I hate that! You shouldn't have to miss out just because you have a child!
We are in the same situation once a year, for my DH's Xmas party. (It is a long story, but the party is not really skip-able.)
I can understand if people don't want to bring *their* kids, but who are they to tell you that you can't bring *your* kids?!
Too bad your DD isn't just a little younger, and you could sling her and go anyway.
Too bad since this your Dh's big night, HE doesn't get to choose to have his DD (and hence his DW) with him there.
I don't suppose complaining to the right person would improve things for future occasions? I know it's not fun to make waves though.
If you don't go, you should still do something really special that night, as a family. (I think if you did show up with DD for a while in a cute little dress, it might change some minds.)