Depending on the blue tooth devices (the transmitter in this case) you may or may not be able to stream to multiple remote devices (Speakers) at one time.. I am not 100% sure of anything blue tooth but not all devices have "Multi-connect"
on the other hand the Crain FM transmitter or the others which compete with it work fairly well unless you are in a big city where there is no vacant portion on the band and can feed the signal to 1,2 or 100 or more receivers, any standard FM receiver is all you need at the remote.
I have used bluetooth speakers,, But never more than one at a time. Also my smart phone feeds it nicely (In fact I have lost the dongle for my computers).