Don't need no stinkin' mixer any more. But I use one most of the time anyway, just in case I have a guest artist or vocalist. Also I could, along with laptop, could get through the night if the keyboard ever failed.
I use this one these days. It is powered by USB, weighs next to nothing and has outstanding features.
http://usa.yamaha.com/products/music-production/interfaces/ag/ag06/

I also have a larger Yamaha mixer, MG82CX, and an even larger Peavey, PV10, for the increasingly rare events where I need them.