We would arrive on a Friday and leave the following Sat..
O.k., good to know. Because that will not give you a full eight days for your visit but seven only. So that would basically leave you with three days for Munich and three for Berlin, with one travel day in between. I personally wouldn't cut down on those few days for greater side trips any further; a stop on your travel day at the most, or a day trip from one of those cities.
I would like to see the contrast between East and West Germany.
Berlin would be the greatest place to see that because you have East and West so close together, within one city, and I am sure there are a lot of city tours focussing on that.
Practically, however, that may just mean that whatever is new is East, and whatever is old, is West, because so much work has been done in the East since 1989. So you won't get a really genuine impression of what the East was like any more. In the 1990s, the East German Autobahn system was the most modern of all of Germany, so that's how you have to think of East Berlin too.
Maybe you can try and find some Plattenbau neighborhoods in East Berlin. Try and imagine living there in pre-1989 times - those were the apartments people really wanted to have!
In order to get a more genuine "East Germany" impression, you would probably have to go to one of the smaller towns farther away from Berlin, which of course is impossible within your given schedule. There, you might still see houses with the drab grey East German plastering, and you might also get an impression of the somewhat depressing situation of those towns, with many young people having moved away, and the economy going down.
The DDR-Museum would probably give you and your children a really good impression of life in East Germany before the wall came down.
does anyone think the German National Futbol team would be playing in
the late March/ early April timeframe
I am really not into soccer, but living in Germany, there's no avoiding it altogether, so I'll try to pass on my basic knowledge to you: Seems you might actually be lucky and have the National Team playing against Brazil in Berlin on March 27.
If that's not within your time frame, have a look at the Bundesliga games. That's what German fans go to on a regular basis, and usually they are really loyal to their club no matter if they win or lose. I would assume that you will actually get a more authentic German soccer atmosphere at a Bundesliga game than at an off-season National Team game.
During your time in Munich, maybe you are lucky to be able to attend a game of the FC Bayern München (they are the guys who win all the time). For Berlin, have a look at the Hertha BSC games. Keep in mind that most games are on the weekend and plan early for tickets since your time frame will not include a whole lot of Saturdays.