[chappyman66]

Be oiled!
If the cars haven't been run the first thing is a tiny drop of oil (3in. 1 works if you don't have anything else) and let them sit  a few minutes to soak.    I would oil the bearings on the motors too but you have to be really careful to get just a tiny drop.

Once everything is lubricated, try rotating.    If it's easier, apply power (probably going to be very squeaky to start).    If it still doesn't rotate, more work is needed and having them done by Christmas is right out.

If you can lube them and they run, you just need tires which are available on auction sites or other locations depending on where you are.