I have a confession to make, and hope I don't get too roasted for it. I was on this thread last night and I took it upon myself to contact the ROH explaining the situation and that it was on mumsnet.
I got a very nice reply this morning., which said!-
Dear xxxx,
Thank you for your e-mail concerning your noting of a posting on Mumsnet.
Unfortunately, we will be unable to help at this time for a number of reasons.
Currently, the Royal Opera House is undergoing a major redevelopment, the Open Up project and therefore we are currently not in a position to donate complimentary tickets or prizes for charity events.
Secondly, we do have a policy of no under 5's allowed in our auditorium.
Having said all that, what I can recommend is the English National Ballet have a wonderful production of Cinderella, entitled My First Ballet - Cinderella, performing at a number of venues around the UK this summer. I have attached the link for your benefit.
www.ballet.org.uk/production/my-first-ballet-cinderella/
I am sorry to not be able to help on this occasion, but wish you the very best of luck with indirectly assisting this young girl.
Best regards,
Graham Boland
Visitor Experience.