Learn a new song and play a fun game
Blindfolds (use neckers). Jelly with hidden bugs, rodents etc, hand-washing facilities and towels.
Pre-make a large bowl of jelly and Angel Delight layers. In each layer, set jelly snakes and bugs, small rubber mice or rats, grapes (eyeballs), plastic spiders and any other bugs you can find. On the evening, teach the Beavers the song of 'There was an old woman who swallowed a fly.' Then tell them we have done a postmortem and they can help, but it's too bloody for them to see. Blindfold them. Then one of the leaders lies on the floor covered in a sheet and holding the bowl of jelly on their tummy. Get each Beaver to feel parts of the body and then ask them to feel inside the old woman's tummy to see if they can find any of the things she swallowed.