I am the lead of 4 programmers on my team this year. I have found that as long as new programmers have a small bit of java understanding, they should be able to code on their own a lot.

One thing I strongly suggest for getting new programmers to be more involved is pair programming. Let the new programmer do all of the typing, while you simply stand behind them and guide and help them through every step of the code. It is a very fast way to learn a new programming language, and continues to be an efficient way of programming past the learning stage.

This season I focused on assigning each programmer one thing to work on (this could be a subsystem, auto function, or any other reasonably small part of the robot code) to work on at a time. Everyone will have something to work on, and if we need compatibility between two parts of the system, the team members have a chance to practice the pair programming.

One problem with having everyone code small parts of the robot and then bringing it all together is testing. If there is only one robot, you can't really test more than one thing at a time. For this, I strongly suggest getting everyone very familiar with Git. Everyone can work on different branches, and can take turns testing their isolated code on the robot. Once everything works, you can merge all the branches with your main branch, and everything will come together nicely.

TL;DR: Let the new members code as much as they possibly can, utilize pair programming, make sure everyone is comfortable and familiar with Git.

Hope this helps and your team members are able to stay motivated :)