Should I let a woman from work care for my son next weekend?

You need to consider several things before you let your son go. Does she drink or have alcohol in the home? Does she smoke in her home? Does she have guns in the home and if so, are they kept locked up? You did not mention your son's age so is he old enough to call you if something went wrong? You weren't very kind in your description of Beatrice so would it really be nice for you just to use her knowing you probably aren't building upon a friendship? Is the business trip absolutely necessary? Does your son have a friend his own age he could with? I have four children myself and would never let them stay somewhere I had never been or with people I did not know extremely well but I have never been in your position before. Good luck with your decision!