Kevin -- If the solenoid returns are common you could also insert
a heavy duty relay in series with the return and add a 20-30 sec delay
in actuating it.  I would add a drain resistor across the relay, say
10K or so, too.  Floating the output of the flip-flops should be okay.
Some flip-flops also have an output enable (OE) pin, especially those
with appreciable current drive.

I have seen at least one of Mike Ames' Violanos and you have a very
nice unit!  Enjoy!

Phil Duclos