Went through your complete requirement and would like to assist you for the same. Please drop me email at - email@example.com so that we can discuss this further.
I can handle this for you. It does take some theme customization, how much of which depends on how you are using it. I am a US based developer and do quite a bit of freelance Shopify development. You can contact me if you like at: firstname.lastname@example.org
I have some experience with customization for Book That App, it really depends on how far you want to customize? Are you just looking for it to be displayed on the home page or are you looking to add/edit features?
Either way I'd be happy to help - feel free to contact me - email@example.com.