https://www.amazon.com/OWI-Robotic-Soldering-Required-Extensive/dp/B0017OFRCY/

Unless you're kinda tech savvy just a kit like this is probably your best bet.

This is REALLY useful, thank you so much!

I suggest some small cups or large bottle caps as containers

While field-stripping and repairing my wife's iPhone 5, I discovered that an 18-count styrofoam egg carton is ideal. You can even label each compartment. :-)

Keep a laptop or tablet with the instructions nearby, as printing them out doesn't allow you to see the comments on the web site,

I... hadn't even considered that, that's perfect advice there.

the first step is to cut all the laser-cut wood pieces away from each other... you'll probably spend a good hour doing it.

This is where I think the kids'll help out the most. I'll cut (wouldn't trust them with a knife), but I can hand the pieces off to them to sand, and they'll happily spend half an hour or more doing just that.

NOTICE EVERYTHING. Usually they point out where they run wires in the steps, but it is super easy to miss that they laid a cable on one side of another part instead of the other.

This is so true; I assembled this last Christmas, and it was one of the most enjoyable builds I've had, but you definitely had to pay VERY close attention to each diagram, they didn't go out of their way to point out if it was a slightly different (but visually similar) piece.

Thanks again for the multiple pieces of advice, I can see where it's going to come in handy in about a week!