The GTR is Nissan's High $$$$$$ Flagship Sports Coupe & a ~Z~ is a unique 2 seater sports car w/bolt on's that can propel it to the Exotic Sports Car Category.
I got rid of my old 406ci/built 81' Z28 camaro when my twins came along-so i know what you're going through......If the money is no object; Go for the GTR,,,,,if you love your ~Z~ & want to keep it as a playtoy,,,consider a slightly used Q50 sedan...same powerplant/7sp.Auto & RWD as the Z w/excellent performance,ride quality,fuel milage & roomy.
I like you putting your Family First,while making this decision...while i'm 49now & my kids are 21; I'm keeping my ~Z~ and enjoying all the moment's i spend w/it...I have just scratched the surface w/bolt on's & the immediate response has been very noticeable.
Good Luck & Choose Wisely....No rock's thrown from me
