Donut usually made with tons of variation including color presentation and taste. Here is my idea:
Make 1 of 30 cm diameter round cake (2 layers) as a base of cake decorating and several 7 cm diameter small cakes (one layer). For this small cakes, you can make one 30 x 40 x 2.5 cm square cake, then cut it into 7 cm round cakes.
Just cover the 30 cm round cake (cut the top round edge to make it round like donut) with soft basic color such as white, pale yellow, pale pink, pale blue or pale purple. (Depends on the age of the person) You can use buttercream, fondant (the easier one) or steamcream (steam buttercream which will look like frosting when it is finished) or you may cover it with melting chocolate which will look more exclusive. Only star-tube decorating needed to cover the bottom side of the cake (if you didn't cut the bottom edge into round) and circling this decoration on top of the cake if you use buttercream.
Then decorate each small cakes into donut look-a-like presentation. Colorful presentation will make decorating looks great by itself. To cover the small donut cakes, using steamcream is better and easier, effective in time (faster). Then you arrange them on top of the big round cake, but give a space for the name. Done.
Wish this idea would help you and good luck. :)