A big event in March which I've just found out about today. Reasons why it may well be important to me to make a good impression. Will be a "smart casual" cocktail party and meal at a large home but the attendees will all be 20-40's and extremely wealthy so probably very well turned out. Many of them will work in City type jobs whereas I'm in a design field. No idea what smart casual would mean under those circumstances! 
I'm 40 had a baby 2 years ago, still carrying a stone extra and tired eyes! Tanner European skin, dark hair. Wine / baby tummy, tall 5'10" size 12-14, curves, long legs.
What can I wear and what can I do between now and then to look my best on the night beauty-wise?