Hi I own a ceramic shop in Wisconsin and I use Apple Barrel acrylic paints from Walmart. The coverage is good and they have many colors. Afterwards spray them (outside) with clear coat purchased at Walmart also in the paint department. It is in a spray can with a clear cap. They are really going to enjoy the project.

Are the ornaments “glazed” – do they have a shiny finish on them? If so you can buy special paints in art stores for painting on glass.. Such as Pebeo brand, available at Michael’s or Aaron Brothers. These are more specific to what you are doing. If you can take the ornaments home, you can bake them in your oven (follow the instructions) and the paint will be more permanent but air drying is good.

acrylic paint. then spray some clear coat sealer (available at walmart or any craft store)