Well, it was a success (except they were 15 minutes late arriving and I am a punctual person! )
I can tell if my old boy likes a person or not within a few minutes, and the little girl passed the test. Groomed him and tacked him up herself. Mother came with us. I think the pony was happy to go out for a change and was nice and cheerful the whole ride, and we even had a trot and a few strides of canter along a grass verge. She was a good little rider!