Protecting low voltage high C capacitor with high voltage low C capacitor
It's not clear how exactly you intend to connect the two capacitors.  If they are in parallel, then they will see the same voltage, which then needs to be safe for the low voltage capacitor.  If you are filtering the spike first thru a resistor and the high voltage capacitor, then another resistor to the low voltage capacitor, it may work depending on the time constants, the max spike voltage, and the total spike voltage-time integral.

Unless you are very sure about the exact characteristics of the spikes, this is probably a bad idea.  How about clamping with a zener or transzorb or something instead?