May 30, 2013 - 6:37 AM
Theoretically you could purchase a 15-day Swiss Pass (there is no 10-day pass or anything else in between 8 and 15 days). It would be about CHF 140 extra for the two of you, which may or may not be economical as you would only use it for the 2 extra days. Also you would have to cancel the 8-day pass you already have which usually comes with a processing fee, depending on the reseller. All in all, I would not recommend that. I would start using the pass on June 7 (I assume you have a pass that does not have a fixed start date printed on it). That gives you 8 days, including June 14, and only 2 days without the pass in the beginning of your stay. The full fare for Zurich (airport, I assume) to Lucerne is CHF 28 per person. If you explore Lucerne on June 6, or at least avoid long travels and expensive mountain transport, you don't need to spend much that day.
Does this sound doable?