Its such a large voltage ratio that you may find a two-step reduction via 12V is
better (more choice of converters). This gives you a 12V rail should you ever need it
too.... Although there can be issues stacking converters if the last one needs high
start-up current.
Another possibility is DC-DC converter down to 8--12V or so, then a linear regulator to 5V,
which means the 5V rail has no DC-DC converter noise on it. This would be a good strategy
for sensitive analog circuitry, but less efficient than DC-DC conversion the whole way.
Most DC-DC converters leave 50mV or so of switching noise on the output, which for
instance can affect sensitive audio amplifiers.
I'm intrigued with having 30V DC as the available power source - rather exotic.