Fiona,
great plan for learning about rockets and forces. Note that the fizzing takes place pretty quickly, so you’ll need some way to stop the baking soda falling into the vinegar until you turn the rocket over- I use a bit of tissue.
Also, get the best vinegar you can, the Aldi or Lidl inexpensive vinegars haven’t worked for me.
I use to offer this course as a face-to-face and we would make these fizzy rockets. One afternoon, after the teachers had left I could hear a gentle popping coming from the materials – the lid of one of the rockets was resting on it, and there was just enough fizz still happening that the lid kept popping off!
A nice way for the children to gently experience the pushing force of the air is to look at this teacher resource from Curious Minds
https://www.sfi.ie/site-files/primary-science/media/pdfs/col/teachers_pop_top.pdf
and https://www.sfi.ie/site-files/primary-science/media/pdfs/col/teachers_pop_top_irish.pdf