The second photo - the one with the young cavalry officer-Can you make out the numbers above the crossed cavalry sabers insignia? The could help identify the unit and what the DI is.
The next photo down with the older couple - the town is written as Naugard. A quick Google search found Naugard is now part of Poland and is spelled Nowogard. Naugard is the German spelling. The medals look like the Russian style to my eye, but are probably Polish.
The last one looks like a military school cadet to me. I say that because the cap insignia appears to be an officer-type eagle, while he is wearing collar disks like an enlisted man, and his sleeve insignia is in the wrong location and an unfamiliar type to be a US Army insignia.
Hope this helps!