What makes implants look "natural" vs. "fake" for a 5'3", 125 lb. patient? Is 36A to 36C a good target? (photos)

After having 2 kids, coupled with aging (now 47), my small but perky breasts are now just small and sad. Yet I'm terrified of having breasts that look "fake" (too big, too round.) From my reading, it seems silicone, under-pec, would be best. Does this sound like a reasonable plan? Are there other things I should think to inquire of my surgeon? (I've saved $ for 2 yrs to do this, so I do have cost limitations).