You could just have them learn with your own models (give them the same units so there are no balance issues) and then have them choose their own from their. If one likes a weaker army, explain that it will be hard to win. I play Wood Elves even though the internet told me not to, and even they are playable competitively. Make sure they know which armies are most competitive but don't pressure them to get those armies.
If you go down to the woods today, be wary