Carefully break a dozen eggs (keep carton for egg storage until Easter hunt) preserving at least 3/4 of the shell (good time to make a large omelette or something)
Wash/clean interior of shell. Let dry.
Paint eggs, let dry, then fill with confetti and glue/top the eggshell opening with colored tissue, "cone-head shaped", over opening. Hide eggs in yard. Let kids find, then break or smash the confetti eggs on each other's heads.
Fun... But as my Mother always said, "Only Outdoors. Not Inside The House!"
(*) Cascarone
\Cas`ca*ron"\, n. [Sp. cascar['o]n.] Lit., an eggshell; hence, an eggshell filled with confetti to be thrown during balls, carnivals, etc. [Western U. S.]
Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.