About Copenhagen: It is a nice place, and especially if you want to see "the free city of Christiania" as well. However, you should be aware that it might still be a little bit chilly even in mid April. Right now, in Aarhus, Denmark, the temperature has not risen up over 3 degrees Celsius. Copenhagen tends to be even cooler, averaging -3 at the time. Stockholm is even cooler I presume. Scandinavia is a good option especially in late spring, early summer, but for mid-April, warmer places can be more pleasant. My next dream vacation was Prague in mid-April anyways.

Omer currently in Aarhus, Denmark