Just my opinion, but I do know something about this, and I hope this helps.
First and foremost, ANYTHING that COSTS YOU MONEY IS A SCAM. When your child is able to model and has the look, money does not come out of your pocket. I don't mean to step on the ideas you've been given by these nice ladies already, but John Robert Powers is the biggest scam of them all. My friend is paying them about $3,000 to teach her daughter to do what mine is already doing and getting paid for. The other suggestion, the organization that you PAY to get your pictures and FIND you an agent, is also, sadly, NOT NECESSARY.
That being said, are you willing to travel? In April of this year, I was referred to an agency in San Francisco and since then, my daughter has done two shoots for Macy's and two shoots for Mervyn's, and she's up for a Leap Frog shoot next. Her agent is WONDERFUL, loves the kids and everything is very professional. Macy's pays $100 per hour and Mervyn's pays $125 per hour, and these are just for print ads! Film ads pay significantly more -- this agency takes 20% commission from print ads and only 10% from film ads your child is booked for.
Please understand, I'm just an average working mother (42 years old and starting all over again with my new daughter), I am not here trying to "advertise" for this modeling agency. The reason I took time out to answer is because it took me a LONG TIME to find an agency that wasn't trying to gouge me. At my daughter's age, they don't even WANT you to spend money on head shots, the pictures I take of her at home are on her current profile. There is a web site that I regularly update with new pictures and that is $9 per month to maintain ($20 to start). Every time you upload the agency is notified by email and they update the baby's portfolio.
My aunt runs a small agency and she's the one who knew a model who was with this agency and so she passed the name on to me when I was looking for one. She said the "organization" that promises to find you an agency gets paid to do what I'm doing right now, TELLING you about this agency, for FREE.
I hope it works out! The agency is at www.jemodel.com. Shannon is the name of the contact for children. On the web site, click on "Become a Model", then click on "photo submissions". Shannon's name is there, along with all the info she needs you to send her when you submit your grandson's picture to her.
Two other agencies I hear good things about, and have actually met other moms with their kids in them are "Ford" and "Models Inc." Every time I go to a "go-see", there are other baby models from those two companies. Of course I'm with JE so I have no idea how much more or less work the other babies get with the other agencies. But this should be a good start for you.
The only thing I will add is that you really have to be able to travel to the Bay Area, I'm lucky I have a boss that is very supportive of this modeling thing, she lets me take off whenever I need to run down there -- which has been about 6 to 8 times in the past month and a half! Busy busy but worth it. The ads she's going to appear in come out in August and I can't wait to see them!
Also want to add that Amy is correct about the short notice for jobs and for the "go-see's" that you do not get paid for. With the price of gas the way it is, you have to decide how much traveling you can afford.
One more thing, Jessica's idea for the Hawaiian Tropics pageant is also legit, I hear great things about it and that they don't "doll up" the contestants like they do in some of the more "obsessive" pageants. It is a fun thing to do, but everyone doesn't win it so if you want a permanent agency and can do the traveling, go with JE.
Good Luck to you, please email me with any questions, I'm happy to help!
J.