I don't think you're over reacting. Actually you're seeking advice which is quite the opposite.

To me it's obvious the Abernethy Trust was unsure if people would have sent their children on this particular school trip if they had been properly informed. It's better to apologize later then to beg for permission first is a statement I have heard in similar cases. I don't agree with that statement. I was ones duped into attending a musical event which kicked off by a rock band playing among other things some Lenny Kravits covers. After a while though the songs became less familiar and before I knew it the singer was holding up her finger and singing about Him.. I wonder why these people always have to trick people into joining their gang. Perhaps they are not as sure about their own religious beliefs as they want themselves to be.