The kids will not only stand still and sing at CIty Opera, they need to sing and dance actually, they are not bored.
In the coming summer, City Opera will organise a Musical called "Cinderella" which targets for 5 to 16 years old kids. Because your kid is only 3 years old, u may go for their new kid's chorus which is organised in the coming July. I will sent my son there too once details are announced.
My friend's daughter is now a chorus member and she enjoyed so much on every Sat night. She also told me apart from Cinderella, the choir members are invited to go to Taiwan for a singing show !!