Some tips
Don't make it all about learning.
Give them a enemy to fight.
Make sure that they always have a clear course of action.
I think that if you rule out humanoids as enemies, then you restrict yourself horribly, so I would not do this.
All in all I'd run a military campaign. They should have some freedom but not too much. Make it clear at first that they are expendable. They’ll feel great when they realize that they've moved from expendable recruit too valuable field agent.
Don't make it all about learning.
Give them a enemy to fight.
Make sure that they always have a clear course of action.
I think that if you rule out humanoids as enemies, then you restrict yourself horribly, so I would not do this.
All in all I'd run a military campaign. They should have some freedom but not too much. Make it clear at first that they are expendable. They’ll feel great when they realize that they've moved from expendable recruit too valuable field agent.