There is one rule to renting cars when going abroad and that is to only get what is necessary. A lot of people see the cars they can rent but could never afford to buy so they take these. This is generally a bad move. A fancy sports car won't fit your wife and kids comfortably; so be sensible. There are many types out there but here is a few really good rent a cars.
1. Peugeot 207: This is a really good spacious hot hatch style car. These are great for a small family - maybe two adults and two kids. There is plenty of room and they are nice and airy so car sickness is usually not a problem.
2. The Smart Car: Yes they're dinky but they are really good in Europe. With the streets in Europe being quite narrow you need a small car that can corner well. The smart car is loved throughout Europe because it just does the job.
3. Chevrolet Aveo: Not one you would think of but this is a large salon car that is always affordable to rent. It is comfortable to drive and you can easily fit the whole 2.3 children set up.
4. The Mini: Again for much the same reasons as the smart car the Mini can whiz around any city with ease. You can surprisingly fit four to five people comfortably in this little beauty.