I doubt there is such a ticket, if the kids have a ticket to put into the turnstyle to enter the park that ticket will be valid for a fastpass.
If they are performing and then allowed to stay in the park they may be accessing via bus backstage and thus not actually have a park ticket. Just thinking back to my drumcorps days when we entered backstage via bus, not sure if that is done anymore.
It could also be that the chaperones are holding the tickets and as such the kids won't have access to them after they have entred the park. Depending on the ages of the kids this may be the case. I was on the bus from BWI to AK with a middle school group and this is what the chaperones were doing. It was the chaperones denying the use of FP to the kids not Disney. I felt bad for the kids as they really wanted to try EE and the chaperones said no to FP they had to wait in line. IMHO they could have just gone with the kids to EE, gotten them FP's and then taken the tickets back for safekeeping. Not to mention that many of them should have been chaperoned while in the park but that's another topic.
Anyway - Hope your dd gets to use FP! I would shoot a quick email to guest communications to clarify, in case the director is misinformed.
TJ