We have a large screen (available to borrow locally) that I propped up with chairs and lit using a couple spot lights. It took some fiddling to find the best position for the lights, but that was a good opportunity for STEM-like experimentation. In hindsight it might have been more fun to find a way to raise the screen, but our event was informal and this worked for us.
|I also included some images of hand positions to try|
I found templates from the indomitable Martha Stewart, copied a few simple shapes from Jill Bryant's Making Shadow Puppets, and used some complex wild animal templates from Paper Made! by Kayte Terry. One of Martha's shapes is a mermaid and I should have foreseen that it would be the most popular by far. TIP: Make multiple mermaids.
As a supplement for taking home I provided a handout on how to make your own theater out of a box or cereal box, adapting this set of instructions from Ladybug magazine. A fun way to pass a grey afternoon.