I can't help you with initial Ca ion concentrations - if this isn't published in literature, you may need to measure it yourself or open a collaboration with someone who can measure it for you.  For the resting membrane potentials, you might find NeuroElectro useful.  NeuroElectro is a semi-automated literature text mining database that contains alot of electrophysiological data pulled directly from literature.  Try browsing that to see if any of the cell types you are interested in have been listed:  http://neuroelectro.org/