Understand what you're saying, Graham – no expectations here, though. I don't mind if she ends up playing an instrument when she's older or not. It's just what she's interested in at the moment, so it'd be nice to be able to give her something to strum/bash that makes a reasonably gratifying noise with no skill required.
@clear, my sister does play the piano – probably only a couple of times a week for herself, but she'll plonk out nursery-rhyme requests from the kids. Plenty of time for 'Play Twinkle Twinkle on the piano' to develop into 'I'd like to be able to play Twinkle Twinkle on the piano', but it hasn't happened yet.
@ScooterD35, I've never played a Strumstick, but I did have a go on a Seagull M4 at a shop over here a couple of years ago. At the time I couldn't imagine picking it up over any of my guitars very often, but it was fun.