Thanks everyone for there input. Here's what I have as a final draft so to speak. I have found a website which allows me to rent a skyline gtr for about $300AUD per day . That's something I would really REALLY like to do. So

We arrive at nrt airport fairly early 7.50am I walk to the car rental desk grub the skyline and take my wife and my kids to Tokyo. Probably the Intercon ana or strings. The other two mother and mate go by train or I come back and pick them up. The more driving I do in the skyline the better for me. I was also going to park this baby at the hotel.

After my day adventure in the skyline I return the car and then probably get around by train for the next 5 days. How's that sound.