Regarding Alternative Sunscreen:
I found this site (http://www.cosmeticsdatabase.com/splash.php?URI=%2Findex.php) about a year ago that I highly recommend if you are interested in finding skincare, cosmetic and oral care (e.g., toothpaste) products that are safe to for you and your family to use. It is a database (called Skin Deep) administered by the Environmental Working Group (http://www.ewg.org/), and it provides a toxicity rating for many of the everyday products you and I use. And, if there is a product you know about that is not currently reviewed on the site, you can recommend it be added to the site for review.
I found their sunscreen rating process to be very helpful, as it looks not only at toxicity but effectiveness of the sunscreen in terms of its protection rating. The sunscreen I use, based on EWG's rating, is Solar Rx by Key's Soap (http://www.keys-soap.com/solarrx.html). I honestly don't know how it would be for children, as there may be some products in there that could be irritating to delicate skin, but it is a chemical-free alternative for sun protection.
Even so, I believe you can research sunscreen for babies/children in the Skin Deep Database and see ratings for different products available. How do I know they are reliable? I don't, necessarily, but I read up on the organization and their study methodology, and they sound pretty good; beyond this, there really isn't anything comparable that I have been able to find elsewhere online. I hope you find EWG as helpful as I have in researching natural, less-toxic skincare and cosmetic products.