First of all you need to put yourself in the shoes of typical tourist. Imagine going to museum and having a choice of renting audio guide device or using your phone for free, many people would go with second option.
So here is first tip – people like to get things for free and they do have smartphones today.
Next on our imaginary tourist (let’s call him Jack) finds that he should install app, well there is nothing wrong about the app but on the other hand why Jack should install app if he is going to use just once ?
As this stage we have Jack who has phone and don’t really want to install one time app, the choice is obvious – a web app.