Sanity check: Input and output filter for a stacked pair of DC/DC converters
The TEL-3 0523 has an efficiency of 74% at 100mA into the full output of 30V (+/-15 volts). Put it another way, it's likely that this 26% power loss will also be present on extremely light loads too.

So, 26% of 3 watts is 0.78 watts and from a 5 volt supply, the current is therefore going to be about 160 mA. 160 mA will drop about 8 mV across the resistance of the input inductor so this side of things looks fine even if two tracos are sharing the inductor.

You might also note that the voltage specification across load is for loads of 10% to 100% and this is a significant clue to something you haven't considered; You'll probably need to load the output of each traco with a load equivalent to 300mW to guarantee the output voltage doesn't significantly rise about +/- 15 volts.

I've fallen foul of this before and cursed myself. Hey it's not a biggy but you'll curse if you haven't left room for this - put this load directly on the output - no point it going after the filter.

Regards the use of the tracos as shown. Been there and done it with no problem (that I'm aware of)! In fact I needed 18V on one job and seriesed the output from a 15 volt and 3V3 (near enough).

I'd make room for a 10nF ceramic across the 120uF caps too. Clearly I can't tell whether this is good enough for your application because you don't really know. I've used linear voltage regulators on the outputs of tracos several times because I didn't know either and I didn't want to take a chance.

Good luck