I would be concerned about whipped cream holding up for that long without some type of stabilizer.
An old German pastry chef in our city used to mix equal parts of whipped cream and Rich Whip together because he felt it gave the taste of the fresh whipped cream along with a certain amount of stability. Rich Whip is a Cool Whip like product.
If this is for an important event in your life I would try an experiment. A tub of Cool Whip vs a 1/2 pint of whipped cream and then a combination of the two. The test won't cost more than three bucks and it will give you some peace of mind.
I guess I am sort of a coward!