For some background I co-founded a social travel app called Jetpac (acquired by Google 2014). I know the space pretty well. We started out to build a new type of travel magazine, but then wound up building more of a data driven content platform. Travel on the web is a very tough business, travel on mobile is easier, but already pretty crowded. Lots of lessons learned, most best told over a beer.
There are three primary monetization models for Travel (sites / content / experiences / apps etc.). Good products build a decent sized valuable audience (e.g. Jetsetter / Hipmunk) or go after a niche audience (e.g. Tablet and Boutique Hotels).
Lead Generation - insert yourself between the consumer and the site where the consumer will make a travel purchase (e.g. book a flight / room / car, buy a travel package etc.).
Advertising - Basically, a slightly less precise version of option one but typically requiring either a good sized audience, or a highly valuable one.
Content - A couple different ways to charge for content:
Blog to book > start with a blog, build an audience, hit some magic number of MAUs, cherry pick content make a book.
Blog to app > same as blog to book, but put the content in a paid app or an app with In App Purchases
Other monetization models:
Guided Tours - Typically the revenue generating feature of a travel / food blogger you charge a range of prices in a group setting. Something like 'Ho Chi Minh Food Stall Tour - $25 bucks per person.
Photography - If you travel enough and you've got great photos, you can make some money (this could be extended out beyond one user to a whole community of photographers contributing to a stock pool which could then be licensed to stock photography player like shutterstock or ghetty images.
If you have the time (and your investors have patience) I'd always go with some sort of freemium (or slight spin on) model. You could imagine an app that give you the top X POIs for a city like San Francisco, then lets you pay to unlock content that's selected for specific travelers (Foodies, LGBT etc.) as an in app purchase.