What you have achieved there is referred to as 'painting with light', and it can have amazing results if you 'draw' around the outlines of things. Now looking at your photos, in Tv mode, have a look at the apertures your camera chose for each photo of differing shutter speed lengths. Learning the inter-relationship between shutter speed and aperture is one of the fundamentals of photography.
Good results, and it does look like the kids had fun!