Option one: Cut each pie into eight pieces.
Since 8 pieces * 5 pies = 40 pieces total, and 40 pieces / 8 kids = 5 pieces, each kid would get 5 pieces (or 1/8 of the five pies).
Option two: Cut one pizza into eigths and the remaining four into halves.
Since (8 pieces * 1 pie) + (2 pieces * 4 pies) = 16 pieces total, and 16 pieces / 8 kids = 2 pieces, each kid would get one half of a pizza and one remaining eigth (or 1/8 of the five pies).
Option three: Cut each pizza into sixteenths.
Since 16 pieces * 5 pies = 80 pieces, and 80 pieces / 8 kids = 10, each kid would get 10 pieces (or 1/8 of the five pies).
Hope this helps!