Where do I place the on/off switch in a multi voltage circuit?
This is not a full answer at this time but it may help you a little.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A redrawn circuit with correct battery orientation and conventional component layout for ease of reading.







simulate this circuit

Figure 2. (a) The usual and proper way to switch a dual supply. (b) Switching the negative leaves 1.5 V permanently connected between the two chips.

Others have pointed out the problems that creating a dual supply with batteries can cause. It's not a good idea. Far better to have one supply and an LDO regulator.