Following an arranger keyboard or even
a MIDI file by a live musician is not
a difficult task for a real professional.
If the skills are up to the task, then
it is critical to have clear monitoring.For the percussionist,I suggest using in ear phones and have the monitor mix set so the drums are playing a very basic pattern. A nice trick is to use only one ear phone and leave the other ear open so the overall mix can be heard better.
(This way the amateur percussion won't play too loud or they will not hear the ear phone monitor and get lost.)
You obviously have a very amateur bongo player. You referred to the percussionist as a him and her? If it's a girl, she had better be great looking or fire her. If it's a man, get rid of him immediately!