Line the base and sides of a 9-inch springform cake pan with parchment paper.
For the whipped cream:
In a large bowl, whip heavy cream and powdered sugar using a whisk until you get soft peaks. Set aside.
For the banana filling:
In another large bowl, mix cream cheese, sugar, milk, and banana pudding mix until smooth.
Gently fold half of the whipped cream (roughly 2 1/2 cups) into the banana pudding mixture using a spatula until combined.
For the vanilla filling:
In another large bowl, combine the cream cheese, sugar, milk and vanilla extract until smooth. Gently fold in the remaining whipped cream until combined.
Spread 1/3 of the banana filling into the base of the cake pan in an even layer.
Spread 1/2 of the vanilla filling in an even layer over the banana filling layer.
Place the 1/4 cup of milk into a shallow bowl. Dip half of the vanilla wafers in the milk and arrange over the vanilla filling layer.
Spread another 1/3 of the banana filling layer over the wafers.
Arrange the banana slices over the banana filling layer.
Spread the last 1/3 of the banana filling over the sliced bananas.
Spread the remaining vanilla filling mixture over the banana filling in an even layer.
Place the remaining vanilla wafer cookies into a resealable food bag and crush with a rolling pin until you get fine crumbs. Sprinkle the wafer crumbs over the top of the vanilla layer.
Place into the freezer for at least 4 hours until firm.
Remove the cake from the freezer about 20 minutes before you want to serve it. Unclip the side and remove from the pan. Peel away the parchment paper from the sides. Decorate with shell-shaped chocolates and palm tree shaped drink umbrellas.
After 20 minutes, use a large, sharp knife that has been dipped in very hot water to cut the cake.