We're not having a lovely time

I learned a long time ago not to make exclamations like, 'isn't this great' and 'aren't we having a lovely time?' on family trips. Even if we are in Disneyland, I know that such exclamations are likely to induce an unenthusiastic response that doesn't just rain on my parade, it pours.
Last summer we went to London for a couple of days. We had a lovely time. On the way home I overheard the following conversation:
Jo:           Alice, what did you like best about London?

Alice:       London.

Jo:           What, all of it?

Alice:       Yes.

Jo:           I hated it.

Alice:       So did I.

Occasionally I forget myself and start to provide a commentary to a particular piece of fun we are all enjoying, only to stop mid-sentence and pretend that I was about to say something else. I try to remember those good moments, rather than articulate them. And if that doesn't work, there's always the camera. Here we are, having a fabulous time in Trafalgar Square. The woman on the plinth was carrying a sign which read 'please be nice to each other.' Niceness and the above exchange between Jo and Alice are the themes of the short story that I am currently working on. So far I've got three sentences, I'd better get on with it!