An X3 or even an X5 sounds pretty much ideal for your needs, although the ride tends to be on the firm side (the X3 is generally smoother than the X5). The Mercedes-Benz ML-Class is worth considering too, as it's stylish and economical if you choose one of the CDI engines. If you want to buy newer, you might want to take a look at the latest Hyundai Santa Fe. It may not have the badge of a BMW or Mercedes-Benz, but it's a very impressive 4x4 that rides well and comes really well-equipped as standard.