Have a read of 'A Fraction of the Whole', a novel by Steve Tolz. Not only is it a ripping and hilarious black comedy, there is a sub plot that has similar executional elements to your idea.
I dare say the tone, characters etc would be very different, but the author pulls it off.
Re your log line, I like the concept, but I reckon the sub text of certain plot elements mean you can leave out some elements that are currently stated, and may be bogging down the log line... maybe something like:
Suspecting infidelity, a devoted wife slowly poisons her children to hurt her husband, on discovering his innocence, she must conceal the truth to save her family and stay out of jail.
But I'm knew to this... so feel free to disregard completely!