I'm making this pie with whipped cream instead of COOL WHIP?

The whipped cream from the can will fall apart withing the first half hour. It doesn't contain gelatin in it to help it keep its shape like Cool Whip does. Even if you froze it the pie would still fall apart with the canned stuff. If you used heavy whipping cream and whipped that up instead then it might work (would work for 3 hours beforehand), but the aerosol ingredients in the canned whipped cream are what will cause it to fall apart quickly.