Discuss the beautiful weather or that fabulous restaurant in town. Suggest places to see or just grab a few drinks and relax. Don't get caught up in documenting the entire experience- live in the moment with your new friend who happens to live in California. You'll have plenty of time to tell all your friends back home who you met on vacation. If you encounter a celebrity while on the job, remember your job.
Famous people rely on discretion when spending time in public.
If you work at the front desk of the hotel they are staying in, maintain your professional bearing. Never reveal their presence or their room numbers to anyone who does not strictly need to know. The same holds true for the wait staff at a restaurant or the workers at the airport. Being a member of the staff may allow you more access to famous people, but this does not entitle you to violate their privacy. You may still approach them for an autograph or picture, but use even more discretion while performing your duties.