My father got married, is it proper to give money?

My father recently got married at the courthouse to his longtime girlfriend. It was spur of the moment (5 days notice) and for the reason to just be legally married. Not to say that they wont be together forever and I know they love each other, but it was just to make it legal. I was unsure whether I should give them money for a wedding gift. Is it proper to give your father money for his nuptials?