Question: Mandaly, in phrases such as: "ti moun yo", "gason yo", "fi yo", nimewo yo Is this fairly much the case in Kreyol for making plurals? Would you say "Kreyol Ayisyen yo" for "the Haitian Creoles", or "Kreyol yo" for "the Creoles"? Am I on track here? Mesi anpil.

Yes :)
You are on track.

As far as "Kreyòl Ayisyen yo" is concerned; it's grammatically correct  as an example -
But since there's one Haitian Creole, you would probably mostly see this term in singular form  (like Kreyòl Ayisyen an)

For "Kreyòl yo"; yes, you will find that a lot :)
some additional examples on top of what you have are:
Kreyòl karibeyen yo
Kreyòl Antiy yo
Kreyòl Afriken yo

Dakò?
Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words