I had a similiar situation recently.
I stopped midway and asked the audience to clap for the little Girl and then her Parents for supporting Music and bring their Little Person along to hear me!!!!!.
Worked a treat.
As you say Kim the little person is only expressing themself and I love to see little People getting into the Music...but....the Parents however.....well....who Knows!!!
It works trust me, nothing like the spotlight to stop it in it's tracks if it is putting you off. The Little Person is left feeling good about Their fun and the Parent(s) are told politely...enough now you have shared the spot long enough....politely though.
Nothing like being a Musician Babysitter...lol...The Music must have been rippin fur the young'in! nothing like a Little Person's taste to make you feel you are doing something right:>)
Best Wishes to You and Mister
Jude