So, I baked the brownies in my round cake pans.
I then "built" the ice cream dessert in my spring form pan. I placed one of the brownies in the bottom, then put ice cream on top and layered again. I topped it with whipped topping and stuck it in the freezer, and once it was frozen I decorated it. I got the decorating idea from this site.
Do you make birthday cakes for your children or do you use a bakery? I've done both over the years.