Half dollar sounds too small for a small rat. The rule is - nothing bigger around than the snake is at the snakes widest point. In fact, if your snake is truly only as big around as a half dollar, 3 large mice sounds like too large a meal to me. How old is your snake? Do you know how much he weighs? A bp that I picture being as big around as a half dollar is probably going to do fine on one large mouse a week, or one fuzzy rat a week.

Steve