Activate CE pin of a LDO voltage regulator with a momentary switch
You can use a JK Flip-Flop to achieve this. By setting the J and K inputs HIGH, you will be able to use the Flip-Flop as a toggle device to set the CE pin on your LDO HIGH or LOW, depending on the toggle state. A couple of notes:

Remember that a JK Flip-Flop will maintain it's previous state when the power is turned off. Having a circuit to reset the Flip-Flop would be helpful if this is not desirable.
Be careful with debounce. Add capacitors to the input if needed to combat this.