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I agree with Ryan, doing it all on one page with the different number of days/itineraries sectioned out is the way I'd go. First, a page actually can rank well for more than one search term, especially when they are so closely related. And second, what is the point of optimizing different pages for different numbers of days and then canonicalizing them to the ten day trip? The canonical indicates that only the ten-day page should be indexed, so who cares whether the shorter trip pages are optimized or not? They won't be findable in the SERPs. Lastly, there is no penalty as such for duplicate content. Google just decides which page is the most useful to show and the others drop out of the index. If your pages are very similar, Google may well make the decision for you and drop some of them out of the index.