SK on the front, slick on the back.
Sometimes I even go bigger in the front as our front forks can take a bigger tire than our rear. 32 seems a bit small a non slick (in dry conditions). Maybe put a 35 or 38 in the front if you need some flotation and/or grip.
Jan Heine wrote up an interseting article explaing why size of the tire is more important than tread on a bicycle, claiming that with the right size and pressure a slick tire had as much gravel traction as a tire with knobs.
In my personal experience, while the breakaway point may be the same on on many surfaces, the breakaway characteristics of a tire with deep tread is much different. Slick tires tend to let go quite suddenly while treaded tires can have large slip angles before finally giving up.