The question changed after I answered, so I'll answer the new question.
My answers are based on seeing the results of 3D printing deployed in a nearby school system, and my own experience as a FIRST Robotics mentor in my son's school system.
Current question's answer
You are ambitious. At the K level, I can see a group project to change a design (such as bracelets), and print the result. This would be done by an adult operating the design software and managing the printer.
At some point, maybe G4-G5, the students would be in more control, with assistance at hand to help jump past barriers that appear (software bugs, clogged nozzles, ...). By G8 the students should be able to handle the whole workflow if they have come up through the program.
It would be great if there were a version of Logo for 3D printing. Maybe there is.
You will need some form of CAD software to make 3D printing useful. Depending on the students, and assuming a small budget, you could look at OpenSCAD (or SolidPython) and OnShape.
OpenSCAD uses a simple language to specify and transform geometric shapes and to perform union, intersection, and subtraction functions. SolidPython is built atop OpenSCAD works with Python IDEs. With the Python language, loops and conditionals are more natural. OpenSCAD is pretty simple, but some people prefer Python. Designs are not "drawn", but are programmed.
OnShape is a cloud-based, traditional 3D design and modeling tool. Free user licenses are available with the caveat that all designs are publicly accessible and copiable, but others may not change your copy. It will be familiar to users of AutoDesk and SolidWorks systems, although the dialect will be strange.
Both produce STL files for 3D printing the designs.
What is the purpose of 3D printing at the school?
Other training really depends on how 3D printing is integrated into the core curriculum. If 3D printing is part of a class in the static analysis of structures, then the class would be providing the training about strength.
IMO, the best training is accomplished by giving students access to the equipment with a mentor available to answer questions. Each student comes to 3D modeling and printing with their own curiosity and motivation, and those are best served by smoothing their chosen path with information and advise.
What can go wrong?
The worst outcome is where money is raised, equipment is purchased, and no one is available to make it work. Or, it works great until the inevitable problem arises, and no one can resolve it. I've seen this happen in a large, well-funded school system. The students get frustrated, and the program loses credibility. The well-off students buy their own equipment and carry on, while those who can't dismiss 3D printing. 3D printing becomes another failed adventure.
Working in any school system is complicated. CORI checks are required. Special certifications and permissions are needed to work on school property. Insurance and liability are raised as problems which block progress. Often nothing is possible without a teacher-on-staff taking personal responsibility and directly supervising activities.
Scheduling prints which take over a few hours may be impossible.
Most problems can be overcome with strong support from teachers and administration.
The most important persons to be trained are the teachers and/or mentors. They will train the students, and the students will train themselves and each other.
The teachers/mentors should be familiar with the general operation of the CAD software, know how to operate the 3D printing devices, and be able to resolve all common problems. Keeping the equipment available is important. Going down for a month is a long time in a school semester.
If 3D printing is integrated into a specific part of the curriculum, the teacher of that curriculum will provide the subject matter training that is being demonstrated through printing. The physics teacher, the math teacher, or the art teacher will use the 3D printing to teach their domain.
Look to the chemistry department for a fume hood to use for ventilation and a fire-proof enclosure.
Consult with the responsible authorities in the school to determine if special ventilation is required for occasional classroom use. Whatever they say, it may not be enough because of parents' fear of plastics.
Have spare parts on hand to quickly bring a printer back online. The ideal spare part is an extra printer -- plus other parts to restore the broken one when it fails. Consider the latency in the supply chain for replacement parts.
Have a purchasing flow authorized that allows spare parts and operating supplies to be purchased quickly. In some school systems, it can take months to purchase materials because such purchases are handled on a semester-by-semester basis. That won't work when you really need a spool of a special color by yesterday. If necessary, look to PTA-like organizations because they may be able to operate more quickly.
Consider using PLA in the classrooms. There is friendly web content about PLA being sustainable, "natural", and biodegradable, rather than the ABS stigma of being petrochemical.
If the upper grades have a community service requirement, allow the 3D savvy students to volunteer as 3D printing mentors to the younger grades.
If your question is about what equipment to buy, it would be off topic as being a question of opinion and recommending specific vendor's equipment. I am answering the question about determining what should be in a proposal.
Like any consideration of acquiring a 3d printing capability, there is some data that must be known before you can determine such a list of equipment.
First, what will the capability be used for? In a school context, it could be used as part of a curriculum, probably not on the topic of 3d printing, but perhaps something else. Or, it could be part of a school machine shop or hobby shop. It could be used by a robotics club, a rocket club, or a theater club. Based on how it will be used at the school, you can determine the next data.
Second, what will be capability be used to print? Based on that, you can judge which devices meet the need.
Third, based on the "what", and a sense of "how much", you can judge the type and quantity of supplies you will need. Supplies for the first two or three years should be included in the proposal.
Fourth, estimate the amount of special staff time that should be needed, find a sponsor within the school who will commit to that time, and estimate the funds required to compensate them.
Finally, roll up a sales document, ideally based on a rubric from the granting agency, which included the benefits, allignment with the grant guidelines, and the costs. Validate the proposal, especially the cost and the staff requirements, with whoever invited you to submit a proposal.
... and remember to actually submit the proposal by the deadline.
Bringing 3d printing into school is a great addition to other educational and engineering tools. With the right support from the existing school staff and a clear vision of how it will fit into the school activities and existing culture, 3d printing succeed in a school setting.