Confused With User Account Monitoring/Setup

I'm not sure what I've done wrong here. This program seems pretty simple and straightforward, but somethings not working right with my user accounts. My husband and I have a Windows User account with a password and I set one up for each of my two boys so I could set them up on NOF to monitor activity separately. I set-up my NOF account under my name and set each of the boys up individually. In the first screen in NOF when I log on, it shows my name to the right as logged in, then on the left it has my Computer then each of the boys avatars and the plus symbol to add another user. Sound right so far?

So this morning when I got to work my husband called and said the computer wasn't letting him into a site and he was under our Windows User account. I signed in on NOF and it shows one of my boys as being online??? What did I do wrong?