While you’re dying the eggs with liquid dyes, you can safely let your kid have fun with wax pastels. The eggs for this technique should be warm but not hot The heat makes the pastels softer and really very nice to work with. It is a little messy but it’s well worth it. You can scrape a little pastel on the eggs for raised patterns.
I saw this technique here and really liked it (I don’t know whether the wax pastels are particularly safe but the eggs are certainly splendid). To make the bowl, I cut in two one of the ornaments I made this winter