Hi there, based on your situation, one of the best way to market your app is cooperating with hotels. With this method, QR codes are the best way to advertise - creating a QR code of your app, all the users can download your app by scaning it. Then post it on the hotel reception and in the each rooms.
Another marketing way is cooperating with influencers, most people like to follow others and be influenced by the words of some celebrities or well-known people. Based on your situation, the influencers of travel are the best choice.
Apply for awards is also a good way to promote app.There are tons of organizations that give prizes to new, innovative apps for their functionality, design, and so on. If you win, the prizes can be lucrative and a great career boost – but even if you don’t, the publicity for your app during the contest can act as free marketing.
Besides promotion, you should optimize your app reviews, which can positively or negatively affect app downloads. Data shows that 95% users will take the app reviews as one of the most important reference factors to judge the app - 88% users trust reviews as much as personal recommendations, which means that a large amount of reviews makes your app look popular and as a result, more people will download it. You can get app reviews from third parties at the first stage, after getting some users, then you can invite them to review your app.
Hope these methods are useful to u.