The lens will only be as good as your ability/proficiency to achieve proper composition, lighting, and technique. I've gotten great pics from a Canon S3is, the kit 18-55is, a Sigma 10-20, Sigma 17-70, Sigma 30 1.4, and Canon 15-85is. I've also gotten some less than good ones from all of these as well.
Your Tamron will do fine, keep it. It's all about the person behind the camera.
I have a 7 month old. With this in mind, think about a quality fast prime (or 2) before an UWA. Despite what other (non-parents) on this board will say, storms happen all the time, and they are far from the most important thing in life and sinking $'s into glass for chasing before $'s into glass for shooting pics of your child is criminal. Your child is young only once and a fast prime is a must in a parents bag IMO. My Sigma 30 1.4 and Canon 85 1.8 see most of the action with my daughter and I ditched my seldom used Sigma 10-20 & Sigma 17-70 in favor of the Canon 15-85is for a walkaround and have zero regrets.