3D Printed Desk Organiser - Nine Year Old

Challenge: For student, who is nine years old and using 3D Printers in the classroom for the first time to produce a working desk organiser and ensure that it was useable for her seven year old brother.  Print was always intended as a gift, hence the bow that is tied around it in the picture on the left of the design.
Background: This student while relatively young has generally mastered the concepts of using Tinkercad and producing 3D Prints.   The student has required minimal tutoring and for the most parts is producing finished prints that are being delivered to the teacher with a brief and information about purpose of the print.  The teacher part of the production process is over as the student has mastered the creation aspect of what she is doing.

Level of Difficulty: Medium - the student is creating a design that has a number of aspects to it, which you can view from the photographs.
The student choose not to personalise it, although she added a 'Keep Out' to the highest tower and add a variety of generic (ie available from Tinkercad) animals and shapes on the outside of the design.  From left to right a Dog, Bear and a small box.    The main towers of the design consisted of three rectangular shapes that were created onto the base, then dragged to size and finally hollowed out.   The student involved in this creation is able to do this within a four to five minute time-frame from scratch. 
Timeframe: This is a ten hour print.  Given the dimensions of the print and the purpose the level of infill already being the default of 20% this would be the minimum required to successfully complete this project.
Size: The base of the design was a rectangle that was 120mm by 100mm.   The depth of the base plate was 5mm.   The animals at the front were 40mm high, the first tower was 70mm the second 100mm and the third and final was 120mm.  The student had listened to advice about the width of the towers and had this a consistent 5mm.
What we would do differently: With the characters at the front of the design being relatively small (40mm in height) the head of the dog snapped off during the 'rafting' removal and had to be re-glued (with super-glue).   The intention was for the box/pot at the front to be useable as a storage device but the practicality was it is too small.    The lettering shown in the photograph is untouched as the removal of the rafting was considered to be too delicate given its size.
Next Step for the Students:  Despite this students age we are looking at ways to extend her by using additional programs.  She has mastered this form of design using Tinkercad and can do so independently.   (This is the same student who has completed 'Sewing Box', Advanced Bookend Etc.