You can always add those diodes later. The output to input one is to protect the regulator in the event the input is shorted, and with any luck you won’t have that happen before you get around to adding it. The Schottky prevents a startup problem you might not have, or if you do there’s a workaround (turn it off and turn it back on again right away).
Added: Oh wait:
With negative regulators and the LM117, there is an internal diode in parallel with D1 from output-to-input, eliminating the need for an external diode if the output capacitor is less than 25 μF.
But with multiple modules connected, isn’t the total capacitance well over 25 µF? Anyway, that diode would do no harm, I think. I’d still add it.