First of all congratulations!
Dont let the worry of your boobs dishearten any of the excitement for your baby!
I had my boys before my op but my first I put weight on really slowly I was kind of strict with my self and my boobs literally didn’t change, my second I went all out ate what ever I wanted and that’s what made my boobs change a lot, my Third I was careful to slowly put the weight on and again my boobs didn’t change I breast fed them aswell.
I think if your careful and put the weight on slowly and even if you breast feed they don’t change to much, people talk about bad experiences and sagging after a baby but I had my op and didn’t need an uplift just enjoy this period it’s the best time and if you look after your body your boobs will still look good after x