trip to usa in december/january

Hi all
I am new to groups etc so please bear with me
We are leaving australia on Dec 6th to travel to usa. We will be
hiring a car and driving from SF to LA. About 10 days in LA/Anaheim
then to San deigo, barstow (to see Calico Ghost Town - is it worth
is??) We have 3 kids age 13, 10 and 7 so I thought it would be good
for them. Then to Grand Canyon via Kingman. Grand canyon for maybe 3
nights then out to Durango - Mesa Verde. Is this worth a look?
Then off to Page, St George for 1 night then Las Vegas for 3 nights.
From Las Vegas we plan to fly to New York and MAYBE drive to Niagara
Falls.
I am really worried about how cold it is over there in winter and also
if it would be too crowded in New York before Christmas.
The shops over here get absolutely mad pre-xmas, so I was wondering if
it the same over there.
Also I wasn't planning on booking any accommodation before I left.
probably only, Anaheim and new York. should I book the Grand Canyon?
at that time of the year.
It was suggested to me to stay in Queens and take the subway as it is
much cheaper than staying in hte centre of New York.
Also where would be the best place to spend Christmas Day, if we were
in new York.
It will be very strange not having Christmas with our family. It will
be the first Christmas EVER we have spent without them!!
Any advice at all would be much appreciated
Thanks
Corinne