I think the letters look good. The main objective is to let Expedia know they have created lots of negative goodwill by changing the T&Cs of the vouchers we have legitimately earned.

What matters more, I feel, is the number of people joining our "cause", which can be seen by participation in the Facebook group, number of websites carrying our story, and whatever other social media we can leverage and most importantly, getting people to buy-in our cause. Imagine the looks on Expedia executives' faces if and when they see 1000 members in our Facebook group denouncing what they have done.