Whenever we have driven in Europe we have had a GPS with voice guidance which really helps in the cities. Make sure it works in Europe and is set up in English! Also, I have heard that you can lease a car rather rent when going for long periods of time which can save on money. I think you will enjoy having a car, but you might want to try the train for a day trip for future reference.

My husband loves to ride trains and in the past week we have gone from Zagreb to Budapest and from there to Prague. (I prefer flying but have to admit it was not bad.) The kids might even enjoy it if you get a compartment. Lastly, I would also suggest some beach time if you can squeeze it in.