If you are thinking about implementing a pay to print service with the 3D printer for kids, it won't be something simple as dropping off a file and walking away at least for the first few prints. It is as much a trial and error process for us as it is for the designer. In library school, they teach us the importance of the reference interview, how to properly cull what a person really wants out of a simple question. If they were looking for architecture books, do they want photography? how to build? famous builders throughout the centuries? Is it a school project or just a hobby?
When a student comes to drop off a 3D print job, questions need to be asked. The librarian will have to look at the design as a .stl file and open it into the propriety software of the 3D printer they have before printing. Cura in the case of the Ultimaker for us, or Cube for our Cube 2D printers. Once the file is saved as a Cube file, it cannot be edited so always saving the original .stl file is important too. This way the librarian can decide if they want to make slight edits without having to call or email the patron asking them to come back in or do they because it is a teachable moment? You'll have to decide.
Questions to ask before they leave:
Does it need supports? If you are building anything vertical, say a house, supports may need to be made (for example: where my finger is pointing) since the printer prints the entire project horizontally layer by layer (think like a house foundation). When it got to the roof layer in this instance, it would have had nothing except the columns to build off (which don't go over the entire area) and it would just spray 3D filament into the air. Supports happen after the .stl file is made because most printer
software creates their own supports that are easier to take off. These supports weren't too much fun cutting out later (it made jagged edges over the house door) but it would just be a matter of some light sanding or wire cutters to make smooth. They are very thinly printed and usually can be broken off by hand.
Can we print it hollow? Printing anything hollow takes up much less time because if you print solid, every inch (except where you made room for the holes) will be filled with filament. Printing in solid (or even strong), will prevent fragile thin items from breaking but it is usually not necessary for most simple print jobs.
Are you sure this is the right size? The concept of MM is foreign to most students which is when I break out the digital caliper and show them the actual size. Most of the time the kids say, "Oh I didn't realize it was that large". If someone just drops off a file, there can be no back and forth. The print will be done before there's a conversation (and may need to reprint).