Elementary kids would love this! I had so much fun because this was experimental, colorful and a tactile experience- all appealing to elementary students.
Shaving cream is relatively safe and clean, I would just be aware of any sensitivities to scent and possibly keep one scent free option on hand.
This is a messy yet inexpensive project. While trays are ideal, this can be done directly on a table. Any daily use tools are usable for mixing color and scraping shaving cream. Shaving cream is the only expense, and a little can go a long way? Maybe I have some things to learn about how crazy kids go on things that come out of aerosol cans though…
Another perk to shaving cream marbling, like with other decorative paper techniques, is that it can be the base for another project. Marbled paper could be cut up for collage, serve as the cover of student made books, journals or folders. As a starting point or an add on, marbled paper can be used alone or repeatedly reused, which is useful for student engagement, recycling/sustainability and supply budget.