Congratulations, Kelly! I've been working full-time on Etsy before and after my daughter was born. I reopened my shop 1 week after I delivered her, since I didn't want to miss the holiday sales. Working full-time on Etsy while you have a new born is doable. For me, the newborn stage was the easy part, but it will greatly depend on how well your baby sleeps, how quickly you can go back to sleep, and what you have to do for work. For example, my daughter slept 3 hours straight from the beginning(it probably sounds awful to you now but it is actually great.) It means I only had to wake up twice a night. Also, I can go back to sleep as soon as my head hit the pillow even after changing diapers and feeding her. So, I was rarely sleep deprived. Furthermore, my work involves sitting on my living room sofa and crocheting, so it wasn't a problem if my daughter was asleep, awake, peeing, pooping, feeding etc. I'm not sure what kind of work you have to do for your vintage shop, but if you have to go out and search for things to sell all day long with a newborn, it may be tough. I was able to work full time until she started crawling, which was about 7 months. Then I had to chase her which means I was interrupted from work every 5 minutes or so. Even then, my daughter took 2 naps a day, about 4 to 5 hours total, so it was more like 6 hours a day work instead of 8. When she started walking and stopped taking long naps, I decided to do Etsy as part-time. For me it was when she was 1 year and 3 months old. Now, she is 1 and 8 months old and I can only work when she is taking a nap(which is only 1.5 to 2 hours,) she is watching TV(which I don't want to do much) or after she goes to sleep at night. I am trying to reduce the number of sales, so I can work and still take care of her.
Sometimes I get frustrated because I can't do what I need to do and time goes by so quickly. Though, I am very happy I could work at home and stay with my daughter. I would have missed so many "first" if I haven't been working at home. There will be hard times because you are doing 2 jobs at the same time, but I'm sure you can figure out as your baby grows.