Make it Easy
Instead of layering the berry mixture separately, gently stir the berries into the whipped topping mixture before spreading onto cake rounds.
Try your family's favorite cake mix flavor instead of the chocolate cake mix. Or, substitute other types of cut-up fresh fruit for the strawberries and/or blueberries.
The whipped topping filling can be prepared up to 2 days in advance. Store in tightly covered container in refrigerator until ready to use.