Has anyone amended tax returns after finalization?

We made adoption-related payments in 2011, so we could have claimed them for last year's taxes but didn't because our daughter hadn't been born yet so there was no child information to put in. Our daughter was born in January 2013 and finalized in September. Our main concern is that we won't have enough in tax liability over the next few years to be able to claim all of the adoption tax credit, due to the fact that I became a stay-at-home mom. We're considering amending our 2012 taxes to claim the expenses we paid in 2011 ($2,100). Has anyone done this, and if so, do we put our child's inf on the return for 2012 even though she technically wasn't alive at the time?