Try freezing the cakes first then they wont crumble, mine usually come from the freezer anyway so I guess I didnt think about it if you just bought them!
These yummy like cakes were gobbled up by a group of children ranging in age from 3-14! The only issue I had in the preparation was with the frosting; even the ready to spread, whipped type frosting made the sponge shells crumble. I put the frosting in a metal bowl and melted/softened it over a hot water bath on the stove. Then I spread/painted the frosting on without much trouble. The nice part about this recipe is that it's easy to vary -- I made batches using different flavors of ice cream and different flavors of frosting. The favorite combination were chocolate frosting with oreo cookie ice cream and lemon frosting with vanilla ice cream (no cinnamon).