Really?
I've had an E46 M3 and an Alfa GT, all with three doors and coped just fine and my son is now two and a half
Plus if you've seen/sat in a G37, you realise its designed for massive Yanks, so the doors are about 10ft long! Easier to get into than most 5 doors
Loads-a-room (seat not forward in this one) - or get the cab and drop the roof