Hi,
you want to visit your relatives in Danmark? Why not have before a visit with your ancient relatives (vikings and anglo-saxons) in Haithabu? On your way, I think ,you take the autobahn (A7) from Hamburg to Flensburg. Nearby ( 15 Km ) lies the campsite (
www.campingplatz-haithabu.de) with a nice view over the fjord “Schlei” to the town Schleswig. Now 15 minutes walk to the new UNESCO World Heritage with the interesting Wiking Museum Haithabu (
https://haithabu.de/de/startseite) and the “Archaeological Border complex of Hedeby and the Danevirke” (
https://whc.unesco.org/en/list/1553). Full of new impressions there is also worth visiting ( 15 minutes by bike) the museum island of Gottorf Castle (
https://schloss-gottorf.de/en/homepage). At least you have walk ( 15 minutes) to the nice town of Schleswig with the impressive cathedral.
Greetings from the border of the Baltic Sea
Axel