It obviously is easier to travel together with another adult people – then, it doesn’t really matter if those adults are members of your family of friends. The most relevant issue is that these people would most presumably have similar approach as yours and would like doing similar activities while on the trip with you. You may be sure that in any European capital you would manage to find something interesting to do for you as well as your friends. Nevertheless, the big challenge may be travelling with children. They most presumably will not be interested in visiting too many museum nor churches. You unquestionably have to pick up attractions for children more carefully. And this text might be helpful – it presents 2 European capitals, that might be perfect to visit with your children.