In March of 2017 (next year) me and my husband are planning a 5 day trip to Las Vegas with friends for my birthday. We asked my MIL if she would be willing to come all the way across the country to watch our son while we are gone. (NOTE: I'm still pregnant and my son will be about 4 months old when we go on this vacay) the reason we asked her is because we are stationed on the western end of the country and both of our families live on the east side of the country. My MIL is the only one who is able to afford to fly and come stay with the baby while we're gone.. She recently asked me if she could bring her daughter with her who is also my husbands sister (obviously) to help her watch the baby and stuff. We both agreed that would be fine considering she is doing this for us. My only concern is his sister. We are not very close and she can be very sneaky and she is a hibitual liar. She is also only 18 but has the mind of a 13 year old. I know it sounds mean but it's not what I'm trying to be. She honestly has problems psychologically. I wanted to install a hidden nanny cam in the baby's room and also downstairs in the living room/dining area so that way I can see what's going on while we're gone. I barely hang out with his sister and I have distanced myself from her to avoid drama she puts herself in. Am I wrong to have a hidden camera in my home? I know if I tell my MIL that were watching then she will tell the daughter also.. I am not looking for bashing comments but I do like honesty, so don't bother  with name calling or acting like a child because the comments will be deleted before I get the chance to finish them.