Gut them, take off any good lines, tabs, bladders, bars, valves and patch of good spare material for any future repairs for your and friends gear. Or give them to me, i'll gut them and bin them for you.
I gutted a pair of lines from a kite to make the lines for my 06 Rhino have better depower, better quick release and a bar that no longer gave me massive blisters.
Else, see if repair guys will give you money for old kites and bars??