Martin is the man to speak to about this ...
I *think* that it will probably make his life easier if you give him a GPX that includes both out and back (though I'm not certain how the comparison software works, so may well be wrong).
As for being unsure which route you're actually going to ride, I'd probably prepare both the ice-friendly one and your alternative, and drop him a line either the night before or in the morning before you set off, attaching the one you've decided to follow.