Given that we have to put things in a couple of weeks at least in advance if staff can absolutely commit or vice versa (just like cadets) they're doing well. So put down all staff to cover all bases, given that you can't add or remove staff once it's approved.
I also think you have to weigh things up. Going back before needing 'permission' (and forms from cadets and staff) to do everything, it worked much better as you didn't have to ask people and cadets several weeks in advance if they're available and then wait for Wing or Region to approve it. A week or parade night before was fine. We have planned things in advance and when it comes to the event work, family and school get in the way and people cry off.
The major flaw of the SMS activities system is its inflexibility post approval. Would you cancel an activity (unless it's shooting or AT) because you were light a couple of staff. I would hope staff in the Corps would be more than able to manage a group of cadets in most situations on their own. For those who will say if something happens you need more than one member of staff, think positive. I have staff on the sqn who flap and spin at the slightest thing and I'm completely unruffled.