What year model is your GO 166?
It may be possible to put some side fins (even something you make up yourself out of
plywood and fiberglass) if there are inserts in the rails of your GO 166.
If not, you can still teach your 10 year olds to sail the GO, but they will have to learn
to "rail" the board, and rig steering (what nearly all beginners use at first) may not work
If you had a larger board (a Start perhaps) you could sail with them on the same board for a few sessions until they catch on.
With only one board, you might be able to tether them (does your GO 166 have the 2 tether holes and insert in the bottom?)..
It's not a "recipe for disaster", but it is going to make something that's pretty easy for kids into something a bit more challenging.
What rigs will you use?
Having a really light weight 2.5 m2 (approx.) rig is even more critical than the board choice.
If your little ones cannot uphaul the rig (too heavy), or if the rig is so small it won't drive your GO board upwind (or even on a beam reach, then you have a real "recipe for disaster".
Hope this helps,