L.S.
Put me in the minority of women here who hate Bare Minerals and any of the loose mineral foundations. First, they are a mess to use. Second, if you don't have the right skin for them, they look cakey worse than anything else you can use.
I love Becca's concealer, as well as Bobbi Brown's. They're both creamy and long-lasting. If you start your make-up routine with a tinted moisturizer over your whole face and then spot-treat with concealer applied with a synthetic concealer brush (or even patted on with your middle finger), you will be able to get a sheer, natural application. Finish with a light dusting of pressed powder over your entire face (if it looks too cakey over your concealer, you have on too much concealer, wipe it off and do a thinner application). and then a nice powder blush. If you use cream blush, put it on before the dusting of powder. Also remember to spot treat the areas around your nose, which can get red, and the inner corners of your eyes to help open and brighten them.
I hope you have a good time at your function, and remember, the only stressing over how your skin looks is you. Don't worry about it - just have fun!