There's a "recipe" for ornaments that look like gingerbread, but are non-edible and longer-lasting (they don't spoil and can be used for years). It's a dough made of applesauce, cinnamon, and white glue. You can Google the ingredients and find several versions of the recipe.
Good old paper or tinfoil snowflakes might be an idea. If someone is ambitious enough to crochet some snowflakes out of crochet thread, those last forever.
I also remember seeing ornaments from the olden days that were printed figures cut out of cardboard, then decorated with sequins, scraps of cotton and fabric, and other trimmings. You could cut figures out of old Christmas cards and add glitter and sequins and such---kids would probably enjoy that.
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