Assuming you're willing to accept the salary that's not negotiable, I think you can say that you're looking forward to the opportunity to demonstrate what you can accomplish, but that before you accept their offer, you were interested to see if they'd be willing to offer another week of paid vacation - in light of the fact that the salary offer isn't negotiable, and see what they say.  But also keep in mind what you're asking.  You're asking the employer to pay you NOT to work for another week every year before you've demonstrated that you can even do the job.  Or you can say something like, "What about training opportunities?" and see what the response is, but I think trying to negotiate a membership in something is going a little too far.  If they offer it, fine.  But I wouldn't ask for it. 

Paul W. Barada

The Negotiation Expert