This is an easy one. For a family vehicle, in my mind there are few options:
Range Rover (HSE if you like going fast)
Need AWD? SUV it is.
Both of the above cars stand head and shoulders above all other competition. Range Rover is the most versatile/safe off-road luxury SUV made, and the F10 M5 has received such lavish praise as to be called by Top Gear: "Currently the best all-around car in the world." Can't say I disagree, for a 4-door, the M5 is about as good as it gets.
My 5-year old son rides around with me in the M3, but I'm a single dad, so no real "family" to cart around other than him. Couple that with the fact that we have no snow here and the M3 was an obvious choice for me, however if I had more people to move, would definitely pick an M5 here.