Is standard licensing for background music for video
is- good enough for a small business facebook ads?
Yes. The standard license does cover most web use, including Facebook.
No matter small or big business but standard licensing is a better way.
Hello @herculerami as PurpleFogSound and Aradyas17193 said the standard license is the one to use in facebook and other social media platforms.
Note that 1 standard license is for one end product and to use the same music track in another diferent video you may need a second standard license.