Which German city should I visit?

My family is visiting Germany for the first time this March, and we would like some help! We are hoping to visit two cities, one of which will be Berlin. As for the second, we're thinking one of these: Hamburg, Leipzig, Dresden, or Frankfurt.

If we go the Dresden route we will probably take a day trip out to Leipzig anyway, we really want to see the Völkerschlachtdenkmal.

For context, German language isn't a huge barrier for us. I'm conversationally fluent, and one member of my family is fully fluent. We should be okay :)

Thank you!!