Oh fun! Yes, I grew up here, and I do love a party...
Re: your ideas, I have done a party Eclipse di Luna before, and it was a good experience, but I remember it getting pretty crowded on the way in and out on a Saturday night. Trouble parking, etc - but that was about 7 years ago, so they may have changed things around or added valet or something by now? Never done one at Carpe Diem but their food is good, and I do like Decatur in general.
In what part of town do you / most of your guests live?
For a dinner party, I like:
The Swan Coach House - did a baby shower there this year, but it might be more of a daytime party place...?
Prime at Lenox has a nice room in the back - but I'm not sure on $30 a head, and it might be too small
McKinnon's Lousiane - incredible service, but again, not sure on $30 a head, this area gets expensive
Seasons 52 - never been to a party there, but my mother eats there all the time and loves it
Leon's Full Service
Parker's on Ponce
I am guessing on price range on some of these off the top of my head. If you give me some info about what kind of food / atmosphere I might have better suggestions!