Caoimhe,
numbers related to space are literally astronomical! A frequently shared “space fact” is that 1 millions Earths would fit into the Sun.
This is actually pretty easy to demonstrate — by putting a scale Earth next to a scale Sun on the IWB (I use helioviewer.org, which can easily generate screenshots).
Show that a 1cm Earth takes up a tiny bit of a 1m Sun (I enlarge the image and then get a cm rule and a m stick to show the size of the image).
Ask – what size would it be if we had 100 Earths this way (x) 100 Earths this way (y) and 100 Earths up (y) – and form a cube from 3 meter sticks.
100 * 100 * 100 = 1 million!
With your spatter stars, the children could be prompted to compare rich star regions where there are a lot of stars, to more sparsely populated areas, and this is actually the case in the Milky Way – there are places with more stars, and places with fewer.