"Wenu" is the possessive pronoun for the plural "you" while "wako" is the possessive pronoun for the singular "you." As far as I know you should be able to use both here.
Wiktionary says that daktari is from Ji/Ma class. Plural is madaktari. Shouldn't this be daktari lako?
Or if it's N/N shouldn't it be daktari yako?
Generally, adjectives describing living things receive the M/WA class prefixes no matter what the actual noun class is. However, N/N class nouns generally still use the y-/z- possessives to show plurality. Daktari is JI/MA, so it becomes Madaktari in the plural. Because of that, the plural possessive isn't necessary. You can tell just from looking at the noun whether it is singular or plural.