So far I've encountered different options and was wondering if there is any of them that should be preferred or is better practice (I'm feeling inclined for 3, but I might be missing something). All three work (tested):
// option 1
Phaser.Actions.Call(this.enemies.getChildren(), function(enemy) {
enemy.speed = Math.random() * 2 + 1;
}, this);
// option 2
this.enemies.children.each(function(enemy) {
enemy.speed = Math.random() * 2 + 1;
}, this);
// option 3, native js
this.