I would just use rubbing alcohol over Windex. It might be safe but windex also has ammonia, dye, and perfume that I wouldn't want to be left over.

As far as removing sharpie from a cart. I've done it many times with rubbing alcohol and the slightly scrubby back of a kitchen sponge. And finish it off with the sponge side. It doesn't hurt the cart and the ink comes right off.