Combine the blueberries, raspberries, sugar, and lemon juice in a small saucepan over medium-high heat and cook, stirring and mashing the berries occasionally, until the mixture becomes a chunky sauce, about 12 minutes. Remove from heat and cool to room temperature.
Help the kids measure out and combine 2 cups of the ricotta, 4 oz. of the cream cheese, and 1/4 cup of the honey in a food processor. Puree until smooth. Transfer the mixture to a medium bowl and let the kids stir in the cooled berry sauce. Combine the remaining ricotta, cream cheese, and honey in the food processor (no need to clean it) and puree until smooth; transfer to another bowl.
Place a crepe on a cake stand or platter. Help the kids spread about 1/4 cup of the berry-ricotta filling evenly over the crepe, then top with another crepe. Spread 1/4 cup of the plain ricotta filling over the crepe. Repeat, alternating the fillings, until you have used all your crepes. Spread a few tablespoons of the plain ricotta filling on the center of the top crepe. Drizzle honey over the top of the cake and sprinkle with the chopped pistachios.