Thanks for the heads up!  Yes, I cannot yet replay to posts :(  The critical issue here is temperature, especially related to things like food poisoning.  Appearance is important but secondarily.

Someone mentioned a balsamic vinegar frosting recipe.  I noticed that it uses butter and not cream cheese.  Butter starts to melt at around 90 degrees F.  Cream cheese, iirc, start to melt at about 120 degrees F.  Why is the butter recipe more stable?

Chocolate glaze....is a worse choice in warm weather or better that some variation of other frostings? 

I will use a half sheet cake pan with a recipe for a 1/4 sheet cake, so each layer of the cake will be about 1" tall.  This will give my cake 4 layers, so more fillings will be needed.  Any suggestions here? Convenient would be using jam (or fruit puree), plain frosting with extra vanilla, coffee (mocha), coconut, plain frosting with sprinkles (not much taste but visually very interesting)  I would like to find at least 4 different flavors for the filling.  Some more background: I live in Beijing.  For Chinese people, the appearance of the cake is more important the taste of the cake.  A special cake is one that: has many layers; many flavors; has fruit; uses writing; ....in general, usually a little busy and complex.  I have seen 12" round cakes covered with 3-4 pounds of sliced fruit.

From what you have said so far...what I have decided...Wednesday night I will bake the cakes and give them a crumb coat of frosting.  I would like to be able to assemble them also, which means that I have to have the flavors lined up for the filling.  I have 3 hours the next morning to frost the cake.  If I assemble the cake the night before I can also frost the sides and add borders to it - that makes 3 hours look pretty reasonable.  Then....wake up at 4 a.m. :(  I would have time to put frosting on the cake and then add fruit or whatever needs to be done...then have the cake sent off at 8 a.m.....probably to be consumed at 9 a.m. Besides the fruit, I am thinking of using things like m&m's, small pieces of chocolate, etc. to make the process go quickly.  Would it be possible for me on Tuesday night to make things like border decorations of frosting on waxed paper and store them in the freezer until Thursday morning?

You are a creative and caring bunch.   The last paragraph I have written contains my time limitations.  Please feel free to make suggestions as you see fit.  If I am being too cautious or over reacting, please feel free to say so :)  FYI: weather forecast for next Thursday is 100 degrees, @ 37% humidity!  highest temp is usually reached at 3 pm....I will definitely push to have this served at 9 a.m.

because the melting point of a substance does not indicate the point at which that product becomes hazardous -- for example chocolate -- it can melt and it doesn't need to refrigerated -- although I hasten to mention that cream cheese in beijing may be completely different than cream cheese in the u.s. -- I don't really know for sure -- and of course no one wants their cake/icing to melt either!

also I don't know what shortening is like there -- here shortening has a melting point of around 120 degrees f -- and can be substituted for all or some of the butter --

the time and temperature at which cream cheese starts to get hazardous is over 30 degrees f for four accumulated hours -- butter used in an icing may melt at just over 90 degrees but it does not have the same rate of rapidly multiplying hazardous bacteria that a cheese does -- that's why I suggested the white balsamic vinegar to create a tangy icing -- if it's available where you are -- possibly substituting shortening for some or all of the butter -- 

I dearly LOVE marble cake -- choco and yellow swirled together before baking then with a coffee flavored filling/icing mmmm --

can you get any flavored oils, emulsions or flavorings like raspberry, lemon, they make a cream cheese flavored oil here, etc.-- something like that could make your cakes tasty without the possibility of the heat taking it's toll like with fruit --

if you can get the strawberries and can dip them morning of without slicing them that's a very pretty decoration -- just leave the leaves on there and dip them like that -- needs to be washed day of as last minute as possible or the leaves start to deteriorate -- some people use different colored  cookies, even those almond flour sandwich cookies everybody is crazy about now the name of which is escaping me...and possibly some edible fresh flowers could be used -- ribbon too --

my other question/comment is that you will need to bake ten of the one inch deep half sheet sized cakes to get to 250 servings -- servings the size of 1x2x4 which is the traditional size of a serving -- was that in your plan? so that would be a cake that is just over a full sheet cake in size -- you would have two of the cakes -- each four layers high -- side by side then the last two layers you would cut in half to stack up and make the last little bit -- but if you are serving 1x1x4 inch servings you can do half that size baking 5 of your one inch high four layer cakes -- 

are you well versed in delivering a cake like this? should be boxed and placed into the car on a level surface -- keep it out of the sun -- things like that

as far as making décor in advance for borders -- you could roll fondant into ribbons, braided ropes or pearls etc. -- and since the cakes are squared off straight lines that could work -- 

chocolate also melts in the 90's