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Hi Lucy,
you already have "Remote Buddy" on your MacBook, which acts as the server on your WiFi network.
For your iPhone and iPad, you need to get "Remote Buddy Mobile" from the App Store:
https://www.iospirit.com/products/remotebuddy/mobile/
All necessary steps to set up the connection between the apps on the Mac and iPhone/iPad are explained inside the Remote Buddy Mobile App.
Getting external IR receivers can indeed be a bit challenging, but if you tell me which country you need one shipped to, I might be able to point you to a supplier.
Cheers,
Felix