According to the Google Adsense Optimization Team when changing to a wider ad format generally will increase the number of ads competing to appear in the unit, which usually results in higher CPMs.

The wider formats allow for more horizontal text, this makes the ads easier to read and more likely to be found and clicked on.

You should test this on only a few pages for a few weeks. If your happy with the results roll it out to the remaining pages of your blog to maximize your earning potential.

Traffic is necessary to determine if the adsense square ads are working for you. The traffic should be made up of people looking for travel information, ie., buyer keywords for your posts.

Hope this helps.

Thanks for your comment. Your point is well taken. But that is why we as marketers must be on the lookout for tools that will enhance our marketing efforts for the reasons you mentioned.