As mentioned above, if you shot on a tripod, this is cake. If not, try loading a few of the images in the progression (3 or 4 for starters, in this test) onto separate layers within the same document in PS. Then, select all of the layers and choose Edit > Auto-Align layers and use the "Auto" option when the dialog comes up. If you are lucky, this operation will effectively align the images based on the background elements.
If you are REALLY lucky, you can select all of the now-hopefully-aligned layers and choose Edit > Auto-blend layers and see if it will automagically create the look you are after. Otherwise, you can then make each sets of figures "appear" in the image by painting them in using layer masks. If you changed your focal length (zoomed) during the progression, you have more work to do to get a convincing result.
Give it a shot. If you post like 3 or 4 small JPEGs of the progression here, we can give it a go as well to better help you.