RC Circuit with Multiple Capacitors
It seems like you're making a simple thing complicated.  You are right about the steady state and therefore the t=0 condition.  For that you ignore the capactitors and you have a simple resistor divider.

Note that after t=0 you have two capacitors discharging accross resistors.  Each does so independently with its own resistor.  From basic R-C circuits you know that each will be a exponential decay assymptotically approaching 0 with a time constant of R*C.  You simply have two of these added together.  The two R-C circuits don't interact since there is no current flowing between them, only within them.  So you're answer is just the sum of two exponential decays.  Yes, it really is that simple.