We used sunscreen on our daughter last summer (born 6/21) but carefully researched the type of sunscreen we put on her. I decided it was simply unavoidable because I like to be outside, and the harm of not using sunscreen was greater than the harm of using it.
You can check them with the database that the Environmental Working Group keeps, which rates all cosmetics for the presence of harmful or potentially harmful ingredients. As a rule of thumb, you want to pick a sunscreen that uses a mineral such as zinc oxide or titanium oxide as the sunblock agent, verses oxybenzone or something like that. I found that Whole Foods had the best selection of highly rated ones (California Baby always rates well but is $$), but the Blue Lizard ones generally rated well too. The database is located here:
http://www.ewg.org/cosmetics/report/sunscreen09/findyours...
I generally go for anything they rate a 3 or lower.