When the kids were younger we used dry beans. The rubbery black playmo stuff was a pain to clean up all the time when it got stuck in carpet, etc... They use it now but they are carefully as they are the ones cleaning up.
Ah, such efficient domestic organisation! My children have to do the crawling-on-the-floor-to-pick-up-any-spare-Playmobil-before-the-Dyson-gets-it routine in our house. That's before I send them up the chimney

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PS a Dyson is a vacuum cleaner named after the brilliant Brit who invented it, manufactured it in Malmesbury, then moved production to the Far East. Global-eyes-asian?