Bar staff hire!

Hi everyone! We were going to use our venues bar staff as they hire them out if needed. We met them recently at a wedding fayre and we were not keen. Not to sound disrespectful. Has anyone hired bar staff in for a DIY event before? We are providing the alcohol. Did you go through a company? Which we would prefer because it will be a contract, Or how else did you go about doing this? My fiancés work colleagues have offered as they say they would love an invite but I think we won’t get the professionalism from them as they just want to be there which is nice but I don’t think it’s the right thing to do. Any suggestions would be appreciated. Thank you.