You're SUPPOSED to ramble here, Selina! That's what this thread is for!
Yes, enjoy your Chicken Zen! I say I have chickens for meat and eggs, but it's really for mental health reasons. There's no better therapy than watching chickens be chickens. Like human babies, they won't stay little for long, so enjoy them while you can!
It sounds like your one rooster-ish chick has taken the role of alpha female, and in the absence of a roo, those duties include watching for predators. I'm curious, do the other little ones follow her around?
I can't say there's absolutely no chance of your kids and chicks passing diseases, but it would be very surprising. As you said, a thorough hand washing, or at least a good squirt of antibacterial lotion, is the best prevention. Germs like E. Coli and Salmonella have a difficult time surviving in dry conditions, so keeping the brooder dry is important. As far as I know, the main way humans transfer diseases to birds is by contact with other birds - especially walking around where another flock has been, and coming home with poopy shoes. (My "farm shoes" never leave our property.)