Based on your query, I would recommend using Scratch for your Halloween monster-making activity. This platform allows students to create interactive stories, games, and animations, which can be easily adapted to a Halloween theme.

For instance, students can use Scratch's extensive library of sprites and backgrounds to create their own Halloween monsters. They can then animate these monsters using Scratch's block-based programming language. This not only encourages creativity but also introduces students to basic coding concepts in a fun and engaging way.

Moreover, Scratch allows students to share their projects with others, promoting teamwork and collaboration. This feature could be used to organize a Halloween monster-making competition, where students can vote for their favorite monsters.

Finally, Scratch is a free platform, making it a cost-effective solution for your Halloween activity. It also offers a range of resources like project ideas, tutorials, activity cards, and educator guides, which can help you plan and execute your Halloween monster-making activity effectively.