The mass choir at my church used to range from 11+ (I don't really think they had a limit on how old, although the oldest was 32)...
Issues we had:
1. Younger members lacked attention span and played too much (sadly some of the adults had a bit of the same problem lol)
2. Parents who were in the choir with their kids were a bet edgy when their children were told what to do.
3. Kids took advantage of their parents being in the choir and tried to act up (which was causing number 2 lol... Cause the director wasn't havin' that!)
4. Young members couldn't understand certain voice manuvers (for lack of a better word lol) and had to ask a LOT of questions which slowed down rehearsal considerably.
Now the age range is 16+ ... All that playin and immaturity has been ccut out and we don't have to worry about the parent-child relationships being strained during rehearsals.
We never had a problem with the youngest members verses the older members as far as arguing over the type of songs we sing. The type of songs we sing are "I Want To Live So....." (James Hall), "Hero" (K. Franklin), "So Many Times" (Dorinda C. Cole), those type of songs. I guess we're Contemporarated-old-skool-gospel-group-choir-type lol.