As far as the reducing haze goes there are a couple of things you can do. There are some filters that can do the job. A
circular polarizing filter (CPL) is one such filter. CPL's block reflected light and since haze is basically light scattering off of vapor and other particles in the air, it can effectively block the scattered light and significantly cut haze.
On the post-processing side, adjusting the levels for an image is the easiest way to reduce haze. Here's a
brief description of how levels work in Photoshop, it's very similar in other programs as well. To make the correction you basically take the left hand slider and move it to the right. This redefines where the black point is in your histogram and increases the contrast in your image. This may not work very well for your photo because the people are already pretty black. Adjusting the levels may make your background look nice but turn your couple into little blocks of charcoal. Anyway, couldn't hurt to experiment a little and see what you come up with.