ArcTeryx Bora 80 for the boys and ArcTeryx Altra 62 for the girls.  Shop around and you can find them for under $300 occasionally.

Got to be one of the best quality backpacks out there.  Have very thick padding on the hip belt and shoulder straps.  I have tried some of the cheaper options out there but they just don’t seem to cut it when the going gets tough.