Families car..must there be seven seats?

Hello, I’m looking for a car for my family. One is 2j. and small is 2mon.alt.e and we want another child a year later. (i.e. 2017). then we are 5per. Then you have to buy a 7seater car if you want to buy a car in 1 month? or it is enough a medium class combo e.g. Passat, Superb, Avensis…. A colleague told me that because of child seat the car must be 7seater. How do you think? but can you get in in 7si. 2 prams?? which car would be ideal? I don’t have a car yet. e experience. If someone already had an experience, please help me. Buget €7000 f.l. 12,000km / year 50/50 Satdt/Autobahn