Video mirroring/sharing between 2 tablets

I have 2 Samsung Galaxy Tab 2 7” tablets which I would like to use as an in-car movie player with both tablets mounted to headrests and playing the same movie simultaneously. Both have the Group Share app which could in theory do this, but the version available for the Tab 2 doesn’t support video.

I’ve tried:
• Using hotspot wifi with a variety of DLNA/UPnP players/servers. I nearly achieve it with Bubble UPnP which functions on the hotspot mini network, but it won’t play on the server device as well as playing on the client device.
• Using hotspot wifi with a separate server device (smartphone) playing to 2 client devices (the 2 tablets). Again this nearly works with Bubble UPnP but it won’t play to 2 client devices at the same time – presumably a limitation of the technology.
• Screenshare app by spring design. Will enable a video to be played on one tablet controlled by the other tablet, but not simultaneously on both.
• Teamviewer – looks like it could work but couldn’t get the app working. Suspect it won’t work on a hotspot or wifi direct network.

Are there any other apps or workarounds which might achieve this? I feel that it must be possible...