To Friend or Not to Friend: Facebook Dilemma

Today in my inbox arrived a facebook friend request I've been somewhat dreading: one from birth mom.  It's not that I dislike her or don't want to have contact with her, but I'm not sure I want her to have access to my facebooked life.

I've been weighing the pro's and con's of accepting or declining.  She'd be able to see how the kids are doing and could keep tabs on them without much intrusion or effort on my part.  But she'd be privy to the ups and downs of life too.  When we go on vacations - she'd be able to see.  She'd see how the kids interact with me on facebook. 

What would that create in emotion in her?  Envy?  Joy?  Anxiety?  Do I tell the girls?  How do I keep the girls from finding out if I don't tell them? How do I stop myself from checking up on Her?

So, I'm not making a decision right now.  I need to think this through first.