The one and only time that we have asked PIL to look after DD we came home and found our house stinking of cigar smoke... WTF? FIL has never smoked in our house while we are there, so why would he do it why we aren't there.

Honestly, i would stay as far away as possible, its just not fair on your kids. Your no.1 job as a parent is to protect them, don't accept any excuses from the in-laws.