i am also making one for my sons school chapel.. the school requested a TALL cake to celebrate the "BIGGEST BIRTHDAY PARTY EVER!!!"
my plan is to do a stacked four tier (was going to do a concaved shape or a topsy turvey, but my test run in fondant tore too much with the shape.)
12,10,8,6 all 4" high, then a fifth cake on top, a 4" 3D crown (red "velvet with a white "fur" band, gold triangles coming out with gems decorating it), all covered in fondant. the four bottom cakes will be a whimsical design (4 and 5 year olds) different stripes on one, bubbles/dots on the next, then repeating stripes and then bubbles again. then topped by the crown cake. each tier will have edible pearls as the border, then wires cascading out with diamond beads or pearls on the ends. i think i may use a cake sparkler or make one large candle out of fondant, but place a real candle inside so the flame can pop up out of it, and be blown out after they sing happy birthday.
my point is to have a really tall, really amazing fun whimsical birthday cake (most kids think a birthday cake is a half sheet cake) that shows them that jesus' birthday is an amazing celebration. he is king!