I agree with the guys, thats a special car and if its in as solid shape as you state i would leave as much original as possible. you can jack the body off the frame slightly to slide new body mounts in. anything else can be done with the body on the frame.
Get it running and driving so you and the son can get a little "seat time". The more you can keep it driving as you work on it the more fun it will be for both of you. Set small tasks at first for the project, things you think the two of you can tackle in a weekend, brakes, steering, suspension (safety first), jacking up and cleaning undercarriage for touchup...etc. Nothing better than hopping in for a ride after toiling over the wrenches. You will be surprised as you see things start to come together.
I restored mine with my daughters help body on frame(pics at link below). The motor was shot so we had to wait to drive 8 months as body work was started. I think if i had took it off the frame it would still be apart, instead i have had 3 years of driving and "finishing" it. And just remember, they are never finished...have fun, be patient and enjoy your Goat.
A frame off resto may disable the car for YEARS and often forever once the owner realizes the time, money and space it will take to do it. A car in pieces value has been destroyed until it is put back together completely. An original car, especially a well optioned one which yours is with low miles is at the top of it's value taking all costs into consideration.