I'm hoping someone will be able to tell me what I'm doing wrong here. Running a 2760 (with an attached WAP) and the latest firmware.

Basically, I want to have a scheduled filter that blocks the kids' iPads from YouTube between certain hours. I've managed to set up the scheduling and the firewall filter, but when I set up URL filtering (in the CSM tab) I'm not sure what to do - if I 'enable' the Youtube block, it blocks everyone without scheduling; if I 'disable' this it doesn't seem to actually do anything.

What should I be doing differently, or is there an easier way?

I recommend contact support for assistance with this because what you're describing should work and allow you to affect only specific IPs potentially.

The firewall filter rule should be limited to the IP range / IP objects of the iPads only.