We did this two years ago but not as far.  We drove from New Brunswick
(Canada) to Virginia, a 16+ hour drive. We rented a car one way so we did
not have to drive two vehicles back home.  Our two kids were 8 and 10 at
the time and when we picked up our westy we stayed a couple of night to
recover form the long trip down and then headed home. We took the "scenic
route" home and drove about 4-6 hours a day for six days. This was about
all they could handle at the time (my wife included).  We had a great
adventure and they still talk about the trip and the things we saw and did
(as do I).  We spent two weeks in Newfoundland this past summer and 4-5
hours seemed to be about the most we could drive and enjoy ourselves.
p.s.  If you don't have a Bently manual, get one and bring it along with
basic tools and don't forget the duct tape!  We are driving across Canada
this summer and I cant wait for that adventure!

Pascal
'84 Westy