Yep, a transmitter will be fine. Of course depending on where you live you may get differing experiences. Areas with lots of local radio stations may interfere more, but I use a Tunecast transmitter and works a treat.
I want to be able to listen to Spotify etc in my car but only have a basic car stereo i.e. no line in line out jack. Should I be able to use one of those transmitter thingys? Any suggestions for best kind or another way to do it? Thanks.