If they were thinking of executing the relatives, sure, I'd agree. But at this point I just can't agree with you yet.
It may very well have to come down to that, if Israel were to commit itself to that tack. I just have a hard time imagining that simply inconveniencing the families would provide much of a deterrent. I don't think that the decision to go on a suicide mission is something that they take lightly, like it's just a big party or something that can be so easily spoiled just by crapping in the punch bowl. I really think it's a serious decision, and it would take quite a bit to deter them from it, if anything would deter them from it.