Any particular one(s) you suggest?
I've looked at a few professional pilot boards but they came across more strongly geared towards those in the airlines and those wanting to be.
There are a couple decent groups on Facebook where questions like this might be more suited. But I would suggest running this sort of thing past other local instructors, if you know some, to see what they think or recommend. You could also call the FSDO for an opinion.
Personally, I'd sign the guy off for the whole trip with the expectation that the student would call me prior to departure on his return leg. I wouldn't be signing someone off on a trip like this unless I trusted their judgment anyway, so the expectation for a call would simply be to have an extra set of eyes looking at the weather and notams in case something popped up.