The practice drills for softball below allow you to simulate the stress the kids experience in a fun and competitive way. One of the challenges I see in game time situations during a relay with a runner advancing is that the kids get very tight and make a bad throw.
Break up the players into two groups. One group has helmets on and stands in line at home plate. The other group has one player positioned at third and one at second. The remaining players on that group stand around the foul line next to 3rd. You will position 3 balls along 3rd base foul line starting about 4’ from 3rd and 2’-3’ between each softball. When you say “go” the runner will attempt to run from home to 2nd before the player at 3rd throws 3 balls successfully to 2nd base. Instruct the runner to simply run through the bag. You will award a point to the group that either successfully throws 3 balls prior to the runner reaching 2nd base or 1 point to the group that successfully throws 3 balls prior to them reaching the bag.
Encourage the players not participating to cheer and yell as much as they want to simulate game time. Rotate each player from the fielding group to 3rd then 2nd until all players have participated and then you rotate the two groups.
When you first run this softball drill the offensive team usually will score more points but as you run it should switch to the defensive side getting the majority. Once that happens you can start moving the balls farther down 3rd base line to keep the challenge.