Your son might like the Maxpedition Vulture II ($170), which combines tough looks with a very practical 3,000 cubic inches of space. It also has comfortable suspension, and the option to attach different Maxpedition accessories.
For your daughter, take a look at Deuter's Transit 50 ($179). It’s a classic travel pack with 3,000 cubic inches of space and plenty of places to safely tuck an iPod or a Kindle. Plus, it's easily adjustable, meaning it'll fit comfortably and it’s a pack she can grow with.