This is going to sound obvious maybe, but why not create your own shade and ditch the flash entirely(or dial it wayyy down just for highlights in the eyes)?
For smaller groups when you must shoot in harsh light without flash, I'd use a diffuser--like a thin foam-core / nylon panel or a "really big" umbrella. Simple and easy... no batteries even!
We regularly use a couple of photographic quality white umbrellas that I found at a conference last year. I don't have the size handy (or the supplier--but I'll look) but they're much bigger and lighter than golf umbrellas. We can easily diffuse groups up to six or so in direct afternoon sun (yes it's that large), or cover direct light through sparse cover.
BTW--Doubles as the best rain umbrella going, if you need it, and a reflector, too!
The group size this works with depends on the angle of the sun (at noon it's going throw less of a shadow!).
I'm sure you could also rig up something in a lightweight panel. Here's a link for a premade panel...though I haven't used this.
http://www.lightingmagic.com/sunpan.htm
They should give you better results than fill-flash (though when you gotta use flash, you gotta--and combining a couple of EX flashes in a portable umbrella works really, really well when you need some directional light. Doesn't fix the noon-day sun, though [img]/images/graemlins/smile.gif[/img] ).
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