It looks pretty reasonable, but you both update and delete daddy.daddy... I think you meant this? (destroying the "are you sure?" menu and the "what do you want to do?" menu)
instance_destroy() instance_destroy(daddy)
(also of course you need to set my_monster to the AMP_ID (index in the Active Monster Party array) of the monster you want to delete when you create the menu that eventually runs mev_pause_monsters_release_confirm() , so the variable has a valid value... I presume you're doing this?)