Post kids, picking a Size

I am 5'2, 122 lbs, athletic and I have 2 children (8 months and 3.5 yrs).  I was a small 34 C pre kids and breastfeeding. I am a 34 B with a bit of a sag in my small breasts now.  I just had a consultation and I am doing silicone gel under the muscle (moderate profile)at the end of the month.  My goal is a full Cish and my doctor said 350 cc with conviction.  I don't want to look fake or like a porn star so I am thinking of being more conservative in my choice and maybe doing 325 cc.  I have read a lot of posts that suggest I should go bigger because that is the biggest regret of woman.  Given my size, I just want to pick right.  Anyone have any advice on on to select a size or trust the doc and push the 350 cc?