Why didn't Cronus kill his children rather than eat them?

If Cronus feared one of his children would do to him as he did to his own father than why consume them at birth rather than kill them- or at least cast them to Tartarus. In fact why did he even have children in the first place if he feared their betrayal? Also, why were his children not killed after being consumed- especially for such a long time as it was after Zeus was grown that he forced Cronus to vomit his siblings. Was there some point to keeping them alive within him?