Bookkeeping and Admin roles are completely different, if a person knows debita and credits doesn't mean that he/she is a good bookkeeper, sometimes there are situations where you need expert advise which an experienced bookkeeper can provide because they are experienced and skilled.
Sitting on two hourses very rarely makes sense.

If you hire somebody to manage both roles you are going to feel stress over a time because in this situation you have to invest more of your time along with that person to manage things in organised way.

I would suggest to hire seperate individuals for these roles because of the price variation, time required to manage specific tasks, expertise etc