My instructor had an interesting way of demonstrating what was a sensible level of cockpit discusion.
We were flying a nav ex one day, after about 10 mins when we were nicely established at 3000 ft and on track, he asked me how work had gone that day, and chatted away, I should have seen it coming really, it was the first time he had ever made small talk.
You guessed it, after 3 mins we were at 2300 30 degrees off track . What a plank I felt.
Lesson learned though. Keep discusion relevant to flying.
That said though I am a great believer of doing checklists out loud. It gives pasengers confidence and I find it helps me not to forget anything. I reckon your examiner will be more than happy to hear you recite them.