All the ideas mentioned are good ones. One other thing I would mention is
to stop the access to the shop as well. I lock on the door at a level too
high for them to reach would help as well.

One other thing I would recommend is to educate them. Even if they had made
access and the power was off, plugging in power tools, access to scary sharp
chisels, and just a TS blade not spinning could mangle little fingers. I
don't know how old these little "1040 deductions" are - but it would never
be too early to teach them.

Just a thought

Jums