"You can make slotted shims to fit behind the knobs -- prevent them being
pushed in so they could turn.  And sweetly explain to the kids that
removing those shims will lead to broken fingers..."

I solved that problem by just turning the gas on at the tank when I was
ready to cook and turn it off after I finished.

I always do that because If there was a leak, I could die of Gas
Poisoning while sleeping.