Hey NCRBILL,

since you still seem to be monitoring your threads on Munich, I just wanted to add a few tips.
I agree that taking a train from Munich to Berlin will be much more fun than flying, especially if you haven´t yet been to the former East and your family hasn´t been to the country. Just make sure that you are taking the train called ICE (short for intercity express), and that you´re getting the direct connection which takes about 6 to 7 hours. The ICE is incomparably nicer than the ICs or ECs (though not much more expensive) and you can have dinner with your family in the restaurant car, if you want.
If you´re chosing to go by train, it would also be best to reserve seats - the trains can sometimes be very crowded. If you´re a group of 5, you could, for example, reserve a compartment with 5 or 6 seats. Otherwise, the cars have a 2-2 constellation with a couple of 3- and 4-seat tables, you can chose between smoking/non-smoking, a children´s compartment, a quiet zone and one with heightened reception for cells.
Pricewise, it depends on the age of your children. They travel for free if they´re under 15, but only if they´re entered in your itinerary. Regular adult tickets MUC-BER-MUC are 200 Euro in 2nd class.
Enjoy your trip!