I agree - I've just recently bought a 5-door car and my 2 boys both still sit in the back - first thing I did?? That's right I engaged the childlocks on the rear doors to STOP them getting out on their own!
This is also to stop them banging the doors into other cars when parked in car parks which is where I park 99% of the time - not by the side of the road.
I've been considering the Clubman for the last few months but I still haven't ordered one - however, the suicide door is not something that I can see being a problem. In fact the way
I normally use the car it will be easier to get the children in and out through the larger 2-door opening. If I'm dropping them off to school at the moment I let them both out through the drivers side which in the clubman will be bigger than the hatch!