Gnil, why don't you just visit your local BMW/VW/Porsche dealer, take the child seats with you and just try it out. Most dealers should be willing to help you to make the right decision.
In my opinion, the new Touareg V8 Diesel is a very nice family car, 0-100 kph in 5.8 seconds, impressive for a Diesel.
The BMW X5 should also do the trick, the new 306 HP Diesel is a monster too.
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RC (Germany) - Rennteam Editor 997 Turbo, BMW X5 M (on the ship), BMW M3 Cab DKG, Mini Cooper S JCW