Offline media access while camping

Casting and streaming media "to" other devices gets complicated. It's easier to simply setup a central repository of media and then have the respective client devices independently connect and play media from it. In a home this would be a NAS device that can serve files over SMB, and with native Kodi apps for the different client device OS in use. The NAS can connects to a WiFi router, and if possible has an Ethernet connection to the Living Room player device (RPi4) as nothing sucks more than shitty WiFi killing the movie mood. Firesticks can also run Kodi natively, accessing the same content over SMB. If the NAS has options for Plex or Jellyfin you also have other options for native player apps with different features, e.g. Plex can serve content on-the-fly at reduced resolution which can be useful for WiFi connected clients that may have lower bandwidth, and kids don't care whether something is 4K or HD .. they care they're watching a movie with cousins.

As the NAS device is running in an environment with less stable power arrangements I'd use SSDs for storage instead of spinning drives. It won't prevent filesystems getting corrupted by will avoid physical drive damage from sudden power loss. Using a NAS and SSDs is more expensive than trying to frankenstein something with Raspberry Pi's and USB drives, but any trailer that size and with 3x TVs isn't exactly downmarket camping so you can probably afford it