I agree 6 and 7 year olds need to have a different set of rules, or should have, but, IMO, 8 and 9 year olds need to play by the same basic rules as H.S. Exception would be shorter base paths, closer pitching mound, having to wait x amount of days before pitching again, etc.
I know in T-ball, and MAYBE coach pitch, the play is dead once the ball gets to the infield and the player holds the ball up in the air, regardless of where the runner is. If the runner is half way to the next base then he gets that base but can't keep going.