I find that a ripe banana works for a short run quite high GI. If I'm racing, or for long runs, 3 weekabix and milk within an hour of the start works for me too, (13 1/2 stone bloke). This helps me avoid the running on empty feeling after half an hours running - lower GI, I suppose.
I used to worry too much about cramp and eating, but the realities of family life meant trying things out, so that I can go for runs at the drop of a hat!
As with any nutrition advice, try it out before risking changes before a race!
I always make sure I have plenty to drink with my food (orange barley water or warm tea).