I get the idea that you wanna make a game that needs to escort as many goblins as possible, but I think there won't be any differences even if you let the other 9 goblins suicide in the current state. You can try setting up the level which needs multiple goblins to pass, such as putting a bunch of switches that need multiple goblins to turn it on. You can also put some cliffs before they reach the switches so that the player needs to be careful not to lose too many goblins.