Hello, could I please get help confirming that I have the grammatically correct translation for the following phrase: "Sleep well, my son"?

I believe it should be, "codladh sámh, a mhic" but I'm not confident that I am structuring the phrase correctly or that I am correctly forming "my son" with the intention of speaking it to him.

Any help that can be provided would be greatly appreciated. Thank you.

Codladh sámh, a mhic is fine.
Literally it is not an imperative (as it is in English) but a verbal noun, so lit.: "good sleep(ing), son"

More literal would be: Codail go sámh, a mhic.