Since you shot this with ISO 100, you should have a lot of latitude to lighten the shadows.
This type of scene will, without a flash, force you to compromise in one way or another -- if you exposed for the people in the shadows, the sky in the background would likely get blown. A fill flash would definitely be useful here. But, without one, you are best shooting in RAW and then using PP tools to adjust. Doing more than one exposure would be tricky because, as has been noted, people are in motion.
Try Frank's suggestion: in your RAW converter adjust the picture to maximize shadow details and load that image into Photoshop (assuming you're using that) and then adjust the same RAW file for the highlights and load that and apply that as a seperate layer to paint over the base layer. Or, you may be satisfied with highlight/shadow tools in RAW or Photoshop.
When getting the shot, remember that the camera (if in evaluative mode) will try to take in all the scene in one way or another. To determine exposure, you want to determine what part of the scene can give you a reliable "reading" and that will give you the best balance of tones, then spot meter that part and adjust your exposure -- either with exposure compensation in a "semi-automatic" mode or by adjusting shutter, aperture or ISO in manual mode -- to "tell the camera" what tone to make the subject (if the subject is relatively dark, use -EV, if light use +EV).
You can also use exposure lock -- expose for, say, the shadows and press and hold the * button while recomposing and taking the shot.
These are certainly challenging senes that we all have to deal with one way or another! Good luck and hae fun!
