Chad,
Chris makes a good point re the leaders in ranking and what are they doing. I would also look for chinks in armor. But, first I would stop what you are doing and back up: Do you have a sales funnel? Do you have a serious KWA? Do you have a sitemap predicated on KWA and UI/UX (Factoring in user habits? Likely user habits if the company is new?). To me url structure comes to a degree as a result of these items.
Once you have those, typically on a site of any size (we have particular expertise in the tourist industries on our dev team) you will have certain issues that you will need to make decisions on based on the clients needs, ui/ux, best seo that really are business decisions and you will likely get right - if you take it in order IMO. But that said, the structure I follow is based on some basic SEO rules - four clicks max, four clicks max, keep it simple for the bot (they all can't be Roger), then: What are the important business KWs I must rank for (destination first or event first or mode first, etc.) I would follow that down the line. Personally, I have never searched on Tour company (ies) nor have I searched on "destinations" or "Sights" so I would not have that in my architecture unless the KWA showed I should. So, instead of destinations for example what are they looking for specifically and can I get that in a menu/ sub-directory etc. Then follow your brain.
Sorry that I cannot give you a do it like this: A/B/C but from the fact you are looking I think you will get this and make it happen. My opinion is that after domain what is the first thing they are looking for that is a category then what specifically within that and then other data for a decision. To me you tell the search engine that you are at my domain...this is the most important keyword here, this is next, and this is the final destination that is rock solid.
Hope this helps,
Robert
