I'd actually do the opposite. Let them use pre-rolled first, then when they actually know and care about how the system is set up, have them set it up the way they like it.

(I am actually leading a machine learning for high-schoolers camp in 2 weeks and we are using Jupyter notebooks so that all students, with heterogeneous backgrounds, will start in the same place and get to the fun stuff fast. Many will never have used Python and will not know or care about 2.7 vs 3, just to give the most high-level and basic example!)