G'day VFRpilotpb,
I grew up in Sydney which is on the coast about 2 hours away from the Blue Mountains.
Depends on where your son is planning on going camping ie, established camp grounds and on regular walk trails or is he going to try and bush bash it? The biggest problem that occurs out there this time of year is people sometimes get themselves lost and possibly come up against a steep (sheer) climb or drop that they try and negotiate. Without proper experience, many of these people usually end up getting a free ride in the medevac chopper.
THis time of year, bush fire risk is not going to be an issue. It's cold and wet up there at the moment. So tell him to make sure he takes plenty of good thermal and wet weather gear. Plenty of bushwalkers who have had to spend an extra night out have come down with hypothermia because they didn't have the right clothing or eqpt.
It is a beautiful part of the country up there. I always make a point of paying a visit every time I get back to Sydney which unfortunately is not all that often these days.