I mean, they're probably all about...five years old at the most, but remember Elanor(elivandrisar)? And the mission that created her? Yeah, uh, Zeb, the Aviator, and Dawn rescued about twenty or so fetuses from that mission. Don't think anything's been done with them besides bringing them safely to Medical (and then presumably on to the Nursery post-birth), though it's certainly possible any or all of the three agents have checked in on them now and again. (ETA: This was June 10, 2016. The mission can be found here. Warning for accidental mass teen pregnancy with no option of abortion (though at least in this one it's due to danger to the parents, not invented legalities). At any rate, there are twenty of them, and the rescued kids should now be about 3-4 years old. I think they were about halfway through gestation when they were rescued (so sue me, I'm skimming), so three and a half is probably closer to accurate.)

There's also Lainduilien, but given she's the (Tolkien movieverse) elven equivalent of, well, a little kid, she's probably not up for agent training either. Not much of it, anyway. (Rescued September 2015 at age 15, so she's now approaching 20, but that's still pretty young for an Elf.)

I also have the three Sato kids, but they're...bother, I need to look things up. I think they're eight and nine years old. (ETA: That's accurate.) Cai Bonnefoy also exists, but he's, like. Two or so. Can't see it working.

No idea if any of that's helpful, but at least it's a bit more information...?

~Z, who's going to edit in some links and more accurate information in a bit (and has now done so).

Also, how does this agent training work, exactly?

I wouldn't dream of depriving you of your bells. Although the flute could be useful after some badfic