Poor MX5, you've totally killed any sense of class it had.
Are the LED's pre-resistored up for 12VDC?
-edit-
Never mind. Series wiring. Just keep sticking 1500uF 16V capacitors in parallel to the array of three diodes until you get the delay you want. Note that you'll probably have a fade on too since the capacitor charging will divert a lot of the forward current initially as they charge.