Subjective: The following part of this article is based upon the editor's personal experiences and opinions, and therefore may not be applicable for all readers.
When attempting to recruit Olwen, Fred, if used well enough, can defeat each enemy unit near Olwen's locked cage with ease. After the children are freed, it would be smart to make sure they escape safely. Oltof might make an attempt to attack the children. To make saving them easier, you can have a high magic or avoid unit drain Oltof's Meteor and Bolting tomes and wait until the Soldier reinforcements stop arriving around turn 16 to open the door.
As for Leif's units, you may need a unit who can attack from afar when walking through the narrow path. You can bring antidotes to counteract the poisoned bows the archers use, but the chapter can be completed quickly enough that it may be a non issue. After that path all of the worst is over. Four Sword Armors are in the open space. The archers in the open space are not a problem, as long as you are not in their path. Oltof has no weapon to attack you directly, but he is protected by three Axe Armors and two Wind Mages. If you are able to, you should steal the Wind Tomes.
If the children escape, you will be rewarded in the next chapter with a Silence Staff and the Heim Scroll.