I would think it would be a fun snack, but knowing mine, they wouldnt eat them anyways. The calcium would be nice additive for a beneficial treat verses something fatty. As said, if your hedgies eat the others(crix & mealies) hornworms arent needed. If they dont eat the others its unlikely they will eat a horn worm either.(or so i'd think)
My hedgies will rarely eat a mealies or crickets, such boring appetites.