I own/play/collect both electric and acoustic guitars, with the vast majority of my stable being electric solidbodies. As a long term investment, and slightly contrary to my own approach, I would tempted to buy an acoustic guitar. The craftmanship and longevity of the design would be great as a family heirloom or something for your child to keep, play and enjoy. You can't beat the organic simplicity of me playing my Martin J-15.
Given that, and their reputation, I would buy something with the Martin name on it. I wouldn't get too hung up on it being a limited edition either, just get the best, highest specced model you can afford. It will be special enough being the year of your child's birth. Choose a main model such as an 000 or D in 18/28/35/48 spec depending on budget.