Not sure if you have plans for traveling to Ghana. But here’s how I went about mine:
I applied for a visa for him to enter Ghana. Applied for his passport in Ghana and got it for less than a week. I did not go for the dual citizen card because I (the mother) I’m from another west African country so I would want him to visit my country as well without needing a visa.
Passport application in Ghana cost about $100 (or even less)
Visa to Ghana also cost about $150
Total cost is almost the same as the cost of the dual citizen card but in my situation getting him a Ghanaian passport made more sense.
Hope this helped