A charity event, a fundraiser, a political dinner, anything that's not a wedding and not quite a party.
The focus of tonight's event is the cause itself. You don't have to worry about offending anyone here or stepping on toes, but you do want to be respectful of the reason you are all gathered together. Respect the fact that you're among people trying to raise money for those less fortunate than yourself. Be a gentlemen, in both dress and behavior. Don't overindulge, and keep your attire on the conservative end.
Simple decision here, go with a black tuxedo, black bowtie, patent shoes, and a white cotton square.
Resist the temptation to over-impress. Show everyone you know what you're doing by dressing in simple back tie and executing with perfection. Try a self-tie bow tie.
Not much to prove here, keep it classy. Maybe you have some cuff links that are too flashy for the office that could be put to good use.