"Dad's name is Juma"
Translation:Jina lake la baba ni Juma
They are BOTH correct - "His name, the name of his father, is Juma." - However, yes, it is unnecessary and "Jina la baba ni Juma." would be more commonly used. (that is if you have mentioned the father before; otherwise the "lake" emphasizes that it is the father of the person you are just speaking about.)