Your Polish is really good! If you ever want to see Warsaw again, I’d be happy to be your host if you haven’t been there for a while, you would be surprised how it has changed
You understood correctly, you need a tablet - buy some cheap or used device, or get it from your grandkids - then setup new Google account (not to use your private account) and purchase the app. Then you configure all the useful information in the application and leave the device in your apartment, for your guests to use it. If I have some time I’ll make a short video with step by step guide.
Anyway, I decided to also release free version of the app, it will be exactly the same, but with some minor limitation - for example it will allow max 2 video guides. This way you can try it for free, or even use it forever if the 2 videos limit is not a problem for you, but the main goal of this would be to see it working, try different settings, see all the features, etc. before making purchase decision.
So, if you can wait few days, you will be able to get it for free!