What a fascinating personal journey your father had. Really like his bio and the FreeSpace page.
In early 1945, the 1st PAD transferred to the province of Overijssel, Netherlands and started to push with the Allied forces along the Dutch/German border. Along the way they helped liberate the eastern parts of the provinces of Drenthe and Groningen including the major towns of Emmen, Coevorden and Stadskanaal. In April 1945, they entered Germany in the area of Emsland and finally ended the war in Wilhelmshaven in Lower Saxony, pretty sure they never went as far as Hamburg. On 28 April 1945 the Division seized the Kriegsmarine naval base in Wilhelmshaven, where General Maczek accepted the capitulation of the fortress. They then remained there until 1947 as part of the Allied occupation force.
Looking at the photo I can see the deciduous trees are not in full leaf so it's probably winter or spring. Also obvious are what look like bunker entrances behind the group, most notably above the head of the fella at second from the right. They could be relaxing in Wilhelmshaven, perhaps in some military facility, though the brick-walled building at left looks quite industrial. They don't appear to be armed so this could well be post war.
A unit diary might provide some clues. Good luck in your search.
