Trace the ghost template onto the white card and cut out 6-8 ghost shapes. An adult does the cutting for clean edges. Use a hole punch to make a small hanging hole at the top of each ghost, 1 cm from the edge.
Paint both sides of each ghost with glow-in-the-dark paint using the size-6 brush. Two coats on each side give a stronger glow; allow 20 minutes between each coat. The paint looks milky and almost invisible when dry in daylight, which is normal.
Once fully dry, use the black marker to draw a ghost face on the front of each ghost. The glow works through the marker: in the dark, the eyes disappear and the whole ghost glows uniformly.
Thread a length of black string through each ghost's hole and tie it to the dowel at varying heights, so the ghosts hang at different levels. Space them across the dowel's length so they do not overlap when still.
Tie a length of string to each end of the dowel to create the mobile hanger and hang from a hook. Before the party, hold the mobile under a bright lamp for two minutes to charge the paint.