HELP - Photography Dilema!!!!!

My best friend has the world's cutest daughter.  I'm not even exaggerating - she's the most beautiful little girl.  She is signed with a modeling agency, and every couple of months, they request updated photos of her since they change so fast at that age.  And I love taking pictures of her - she's so photogenic and she has the best personality!  She's a real DIVA at the tender age of 20 months. 

Photographing babies/toddlers isn't easy, as I've learned.  They move and squirm, and they never look at you..... never smile when you want them to, etc.  So for every 100 pictures or so that I take, about 5-7 come out decent.  I even go the extra mile and I edit the pictures to enhance them, or play with them to make them a little more "artsy."  And I do it because I love my best friend, and I truly love taking pictures of her daughter - Alexis (Lexie). 

There's another lady I work with - and she has 2 kids - 10 and 7 years old - and they are also beautiful children and signed with a different modeling agency.  I've done 2 photoshoots with them.  They're GREAT kids.  Their mom actually paid me to do it - even though I didn't want or ask for anything.  She knew I wouldn't take money from her so she got me $75 worth of gift cards the second time I did it.  To be honest, I sort of approached her about taking the photos the first time - I wanted to get some practice with someone other than Lexie.

Now the dilema.  My best friend posts the pictures I take on Facebook, and (naturally) everybody loves them.  I was contacted my a mutual friend to take some pics of her son Brady (also signed with a modeling agency).  She said she has a hard time getting pictures of him herself, and she was interested in having me take some for her to send to the agent and also for their annual Christmas card picture.  No problem - Brady is 4 months old and it would be great for me to get some more experience.  I'm supposed to meet with her this Saturday morning.

Well - my best friend called me tonight to tell me that a friend of hers (who I have met a couple of times but wouldn't consider myself "friends" with) is going to e-mail me to find out how much I charge to take some pictures for her.  Well, that brought up a good question...... what do I charge?  I'm not an experienced photographer.  I do it for fun, because I love doing it.  I consider myself decent at simple editing, and great at cropping - which I think definitely make my photos seem better than they actually are.  But how much is that worth?  And if I am charging people - shouldn't I really have a better idea of what I'm actually doing? 

Any ideas out there for how much a photo "session" should go for?  I wouldn't provide any prints, but I'd give a cd/dvd with copies of all the pictures and edited versions of the ones I think came out really well (or ones they request to be edited).  I guess the real question is - how much is my time worth to do something I love to do?  Figure anywhere between 1 to 2 hours for the "shoot" and then an additional 2 hours worth of editing.  I HAVE NO FREAKIN' IDEA!!!!  Any ideas?  Help!!!