I've always kind of worried about LLL's list of nontoxic terrarium plants, for one they list natal plums, which have giant thorns about 2 inches long, and then they list Cortaderia selloana which is an eight foot invasive grass with serrated blades that can easily cut your hand. While they may not be toxic, the majority of plants on that list are not suited for terrariums.

As for the Crotons, it would depend on what they were going in with. Is it a frog tank, or a lizard tank where they are more likely to snack on the plants?