I am an SLP as well as mother to a son who is nine with a cleft lip and palate. This area is my passion If the child's placement is correct for the target sounds, there is nothing you can do about nasal emissions. There is no way for the child to control emissions through their nose with a fistula and they should not be expected to. If you find that the child is using correct placement and still having emissions, I would explain to the parents that you cannot do anything more until the fistula is repaired. I think for kids with clefts this can also become a self-esteem issue. If they go to speech and never improve it can lower their confidence. Try as they might, there is nothing they can do about something that is structural. Keep in mind the child also may have V.P.I. which is another thing an SLP can't control.