Here is my Workaround solution to the 1 Laptop/Tablet Source and Multiple BT Headsets/Speakers Scenerio without spending a dime or looking for any HW addon.
below is the solution for 2 BT headpones connected to Laptop.
1. Install free software 'SyncPlay' in the Laptop.
2. Run 2 instances of Syncplay one as Server and other as client with both attached to VLC Player.
3. Set the audio-device of Server-VLC to BT-Headpone/Speaker-1 and audio-device of Client-VLC to to BT-Headpone/Speaker-2. [using VLC Menu->Audio->Audio Device]
4. Make client-vlc minimized,
5. Set the Audio Path directories in both the Sync Player to same Folder location. [Using SyncPlay Menu File->Set Media Directories]
6. Play audio/Video on the Server-VLC, and Control the Client-VLC using the Client-Syncplay. If you are watching Video remember to set the Video_track of Client-vlc as disabled, Viola.. u are through.
Sometimes you need to sync the client-audio just by moving the slider control of the server-vlc. You can add more than 2 bluetooth speakers/headphones with this solution, just need to add number of syncplay clients and set the respective audio-device in the vlc instances.
This is how I watch movies with my wife using 2 BT-Headphones and Single Laptop in flights or in similar situations.