Outward I would suggest Day one go around Dutch Coast and stop at Lubeck /Laboe , next day a bit of motorway but will give enough time to stop at Rostock if you are into U Boats (Type 21) then on to Rugen (Prora ), ,we then went on to Peenemunde the next day and stopped at Anklam (interesting history ) , then make your own way back
You may want to stop at Rechlin. This was the German test centre for experimental aircraft and was an airfield from the earliest days of flying. There's a very good museum there.
Since we are in the suggestion of stuff to see and do, I’ll lob in a visit (it won’t take long) to near enough where Montgomery took the surrender of the Germans at Luneburg Heath.
Depending on which way you go, you might well be going straight past it, just before you cross the river Elbe.
There’s not too much to see, beyond a commemorative stone. But, you and your mates, will be standing (near enough) on the site of one of the most momentous moments in history.