There is no historical evidence that suggests what the Druids did with their cats on Samhain specifically. Samhain is an ancient Celtic festival that marks the end of the harvest season and the beginning of winter, and there is limited information about the specific customs and rituals practiced during this time by the Druids.
However, cats have played an important role in Celtic mythology and folklore, and were often associated with witches and other supernatural beings. It is possible that cats were included in some of the Samhain rituals and beliefs, but there is no conclusive evidence to confirm or deny this.