blocker? msn tracker? trying to keep my kids safe.?

hi i am a single dad who works from 10-6 or later. i have my 16 year old son at all day now that school is out along with his younger 12 year old sister. the older one 17 has sumemr school but she still is home more than i am. i noticed one day under history some links that were there. i believe it is my son but havent talked to any1 about it since am not certain and wouldnt want to ebaress the wong person. i need a progream whre it keeps track of all history msn chats, websites emails kind of what they have at my friends work where he cant fool around. i am worried my son is in an ameture gang taht looks to be getting serious but he is in denial my daughter afraid to say i think is a bit promiscuous and the younger one well she is on msn 24 hours and when asked what she talks about with who she stutters to tell me. they all hide it from me because i am their father so its hard for them to tell me. is there a program that will keep an eye on what my kids do at all times. thanks