Power Supply for Bluetooth device
Most engineers would now use a Flyback Converter in most similar cases.
It's similar to a buck/boost converter, except it uses a flyback transformer in place of the single inductor.
While it adds a bit of complexity, and loses a bit of efficiency versus the buck/boost, it adds electrical isolation, which is often required by either regulations, or design/safety specs.
While an analog Vreg (regulator) could perform this job, they are usually only used when absolute stability of the output voltage is paramount, and for large voltage differentials are often employed after some form of SMPS converter (buck, boost, buck/boost, or flyback topology) as a "smoothing" for the output.
Depending on the exact stability required by your components (relays can throw a LOT of noise into a circuit when switching on/off their control coils), you would have to make decisions as to how many &amp; what size of storage/decoupling capacitors will be adequate for smoothing the output from an SMPS, and if a Vreg would be necessary (or even beneficial) as a "final smoothing stage," should you choose to use the SMPS topology.