If you are willing to leave continental Europe, but stay in the union, then I recommend a trip to Liverpool, in the United Kingdom. The city has many tourist attractions, like The Beatles museum, a large observation wheel, and a beautiful newly built outdoor shopping centre named Liverpool 1, among many other things. There are also a wide range of restaurants, and night clubs. There are very good transport links also, to take you to many other places. Like the Roman city of Chester, and the vibrant seaside town of Blackpool, famous for its nightlife! All these things can be enjoyed with your family. But our city is rather unique. The river runs right along the city centre, and many attractions are alongside it. You can see tankers berthing at Tranmere from the city, large RoRo ferries to Belfast and cruise liners that berth dead in the city centre. To photograph the cruise ships, take the famous river ferry, which passes very close to them. This is also an activity to be enjoyed by your girlfriend also as the tour is very informative and stunning views of the city can be seen from it. But the cruise ship year here is only from May to September. And check the dates of arrivals. One final point is the town of New Brighton, a bus ride away from the city. This directly overlooks, and is extremely close to the container and bulk terminals at Liverpool, and when ships leave the dock, it is within easy reach of your camera. There is things for you to do with your girlfriend here also, there are some very nice restaurants at the seafront, and a napoleonic fort to explore. There is also a new cinema.
Where ever you choose to visit, I wish you both a pleasant holiday.