a Club Car should have six 8V batteries for a total of 48V.
you either need:
voltage reducer (wire across 2 batts to convert 16V to 12V)
voltage converter (wire across all batts to convert 48V to 12V)
or an accesory 12V battery and no reducer/converter needed
once you get down to 12V, you need an inverter to convert 12V DC to 110AC
all that is too much trouble (and expense) for some christmas lights.
I was looking and came across this website:
battery powered LED strings: (only require 3AA batts)
take a pic when you get done!