This kit looks like a wonderful teaching toy, but getting it to work has been mildly frustrating. I wouldn't let that stop you from getting it, but it might be a wise thing to buy an extra and put it together before introducing this to your kids, so that you know where the potential pit falls are. Having another kit for spare parts isn't a bad idea, either.
I just finished working with a couple of young girls (9) I tutor, putting together a Drawdio. Predictably, we had some problems, but that's part of learning. There were two problems, though, that I think could have been avoided.
First, we mounted the speaker directly to the PCB following the suggested method. Later, when one of the girls dropped the drawdio on the floor, it hit on the edge of the speaker and the contacts on the speaker itself sheared off. Fortunately, I had a second Drawdio kit. This time I used the wires to attach the speaker, but I also glued them to the back of the speaker using Gorilla glue (made from the finest gorillas). Gluing them will, I hope, reduce the force applied to the contacts. I considered gluing the speaker to the PCB as well, but figured that leaving it loose would allow the speaker to move the next time the device is dropped, reducing the force of impact. I would suggest using higher quality speakers, if possible, and/or recommending that the user glue the wires down to the back of the speaker as I did. (By keeping the wires short, you can wind up with the speaker in the same spot as it would be if you mounted it on the PCB. Just be sure to cut the wires to length after you solder them to the speaker and glue them down.
The other problem was getting the tack in just the right spot. Because the end of the pencil is painted over, it's hard for small hands and inexperienced eyes to make sure the tack hits the graphite. I suggest adding an optional step where the user cuts off a millimeter or two off the painted end so they can see where the graphite is. Alternatively, they could simply reverse the pencil and put the tack in the other end.
I think it would also be a good idea to add a briefer from of the excellent instructions you provide, perhaps a recapitulation at the end of the instructions with links back to the details.
Finally, the one problem I haven't been able to solve is that no matter how I place the tack in the end of the pencil, we don't seem to get a reliable connection. Everything up to the graphite tests just fine, but we don't always get sound out when touching the tip of the pencil or the drawings. (The other hand is on the copper tape.) I've tested with my continuity checker, and the graphite path from tip to tack seems fine. So, I'm confused about that.