Did you make your own henna or buy it from a store? I have my fourth graders work on a henna project to work with different kinds of lines and patterns, but I wanted them to have the actual experience.
Leigha, the first time we did henna it was from a kit I bought in an art & craft supply store. It was a powder that we mixed and put in a special bottle with a drawing tip. After that, we ordered a bunch online. It was more "authentic" - comes ready to use in a cone. Anyhow, I did NOT use the actual henna with my students, though I have had them do henna designs by tracing a hand on skin colored paper and then mixed henna colored acrylic paint and put it in an empty glue bottle to simulate the experience. Another time we just used markers.I do not think having the kids do actual henna on their skin is a good idea. If you do decide to do it, I'd be sure to get parent approval, as you might find some objections, possibly even religious objections. Good luck!!
How fun! I keep thinking that if I get married, I want to have henna designs on my hands that day.