You sound like you are more comfortable with design software than I am...I started with Sketchup but found it to be very difficult for students to learn independently (which is my goal in my MakerSpace club...I do not have the time to do a step-by-step how-to with software due to the controlled-kaos nature of the club). I found much more success with the web-based program Tinkercad
https://www.tinkercad.com/. I needed to set up accounts in advance and have my students share them (due to the way Tinkercad handles CIPA/COPA/FERPA
restrictions with students under 13) but it was well worth it and easy to get kids designing right away. 123D was good too, I liked Tinkercad better though. Easier to save and share files for printing.
Just my 2 cents!
Julie