For long term reliability the 12v + 24v transformer is the best option switching supplies are efficient but prone to failure I can contest to this with the number that have failed for me even with expensive telecommunications grade units I have used, yet I have transformer linear type units that are more than 30 years old that are still performing as when they were new some have been on 24/7 all that time.
What was needed was to get the 24v and 12v on different windings as spikes induced through the transformer will be even on the other winding and can be filtered out a direct path can not be found through the logic, blocked by transformer and op-coupler. You can place the same resistor and capacitor as on the triac across each of the 12 + 24 volt windings of the transformer now for your +5v supply these are ok I have 4 and are working well http://dx.com/p/dc-3-40v-to-dc-1-5-35v-voltage-step-down-transformer-module-154907 the parts would cost me 4 times as much all you then need is a small bridge rectifier , a 1000uF capacitor and fuse.
Regards Paul
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