This is my 1st wedding cake, that I am delivering to a venue at the end of May.  Air conditioned, nice venue. But I'm concerned.

I have a bride that wants a layer of white chocolate cream cheese buttercream in the middle layer of cake and it would also be a thin layer under the raspberry preserves in the other 2 layers .  Cake would have white chocolate ganache dams with ea layer, covered ganache and then fondant.

Is this a bad idea? Would it not stay cold enough even wrapped in all of this in the fridge overnight until put in the car?

I am thinking of offering to change to white chocolate buttercream ( sans the cream cheese).  I bought the cream cheese emulsion flavoring as an option, but .... well, it's not the same of course.

Any help would be greatly appreciated.

i would do it sans cream cheese if that's possible -- unless your recipe is specifically designed/certified to be able to be out of temperature it has only a 4 hour lifespan to be out of temperature ie over 40 degrees f -- so if you can talk the bride into deleting it it will make your life much easier -- after 4 hours the bacteria have multiplied enough that the icing becomes hazardous to the very young very old and people who  already have chronic conditions  --

Just read the bride what K8 wrote above.  There is all sorts of data/studies online about perishable ingredients.  A possible solution is to mix your ganache/butterceam with shelf-stable, Duncan Hines Cream Cheese frosting.    I use a 50/50 mix of DH Cream Cheese and my buttercream recipe for filling my red velvet cakes.  Of course the taste isn't as good as REAL cream cheese, but it is safe. 

Unless you have a specific recipe approved for use in your business (or cottage food act) for a shelf-stable cream cheese frosting/filling, it may be prohibited by law.  (Obviously, depends on recipe, state, etc. etc.)