I quite like this as a break to usual nets...tend to do these every few sessions with my juniors. Good to be on grass, you can set fields relative to the respective batters, you can generate a bit of atmosphere in the field and banter from the keeper. What we did last year was when the batters went off, they then went into the nets for some throw downs or you take a bowler off for a session as well. I was lucky enough to have Mark Robinson run a few of the junior sessions and this is the format we used for those.. For me its important to keep the sessions varied and avoid the nets with groups of bowlers standing around (including those who dont really want to bowl ) and batters just trying to smash the ball back as hard as they can