Naming ceremony: is ₦20k a fair gift from a cousin or will it look like an insult?

The baby belongs to my father's younger brother's son, so a cousin I see twice a year. I'm a corper with an allowance and a rent. I can do ₦20k and maybe a gift bag. My mum says ₦50k or do not go. What is normal for a cousin in your family, and does the amount matter if I show up and help carry the plates?