Original Post Followup
First, thank you all for your detailed and impassioned comments. You helped us confirm a lot of what we had already been thinking, but also gave some good advice and added a few issues we hadn't thought of specifically.
Second, my apologies for not responding sooner. Getting caught up in all the issues above, while trying to manage a few viruses with us and our kids, settling our new born, and getting work done too were pretty taxing on our bandwidth. although i know in this day and age, most people expect instant replies, so thanks for your patience.
Third, to clarify, i am the husband, so perhaps my more rational over emotional side is manifest in my post here. Like Elle, Cara and others, my wife wanted to fire both of them on the spot. I knew this was serious, but as mummymoo, Gracey, and others also expressed, i was not convinced she had done this maliciously or even realized the potential danger to what she did. I think I believe as Elle wrote -- "For all we know the helper could have been overworked, overtired and in desperate need of a break so she did something that while very bad and inexcusable may in no way have been intended to intentionally harm the baby." And I do know quite a few parents who would have no issue of giving sleeping aids (e.g. benedryl) to kids to help them sleep on a plane or in certain circumstances.
Our bottom line was that despite the good work she had done for us in the past, and despite my view that she was caring and our baby boy was attached to her, she should have known that this was not an acceptable thing to do, and even if the medicine was not harmful, it was the principle of what she did that would make it very difficult for us, and especially my wife, to trust her again. We fired her the next day.
That next morning however, we did give her one last chance to change our minds as we discussed the whole issue with her again in depth, and gave her opportunities to explain and commit that she realized the magnitude of her error. But although she expressed some regret and apologies, we didn't feel sufficiently moved to change our minds. We noted on her release form what she had done, to make her next potential employer aware of the issue. [That being said, and a credit to how she can present herself well, she was able to get a new job with an expat couple within a few days after our release.]
Our second helper, we were thinking of letting go as well. But as she had just started working with us, had shown a willingness to follow our instructions, and as we knew it could take some time to find replacements, we had a talk with her as well, and will see how it goes for the time being.
Again thanks to you all for your comments. We've learned a lot over this incident, and hopefully we can be more careful and discerning for our next picks, and the training and supervision required to not let things get out of control.
[need to do more research on this, but a few interesting links]
http://answers.yahoo.com/question/index?qid=20090713081023AAhvO84
http://voices.yahoo.com/why-its-not-safe-give-young-child-sleeping-9052257.html
http://www.childrenscolorado.org/wellness/info/news/51505.aspx
http://www.consumerreports.org/health/free-highlights/manage-your-health/benadryl_babies_sleep.htm
