Can I use 100μF and 47μF as input and output capacitor, respectively, for regulator LM7924CT?
I would recommend using the values given in data sheet if possible. Order some more caps you will surly need them sooner or later. The data sheet also states:

"If large capacitors are used, a high current diode from input to output (1N400l or similar)
should be introduced to protect the device from momentary input short circuit"

Not sure if this is valid when you are using it as a single supply.