It's been our pleasure to work with the Butterfly Pavilion for many years now to help them educate their visitors on the beautiful (and creepy crawly) invertebrates and other creatures in their exhibits.
Butterfly Pavilion's substrate of choice for displays is typically 3mm Sintra, which can stand up well over time to lots of little fingers. For outdoor signage, we've used Dibond - aluminum on the outside with a PVC core to make it lighter - with a UV laminate, and for shorter term use items, foamcore and gloss inkjet paper. This work has ranged in size from 3.5" circular 'pucks' to large (5' x 4') contour cut signs.
The Butterfly Pavilion's imagery is beautiful, the cause is stellar, and the critters are, well, very crittery.