I know they were three and five. I am just wondering why you think it is ok for them to look at VS catalogues or to poke around ladies changing rooms while it is not ok for them to see a woman breastfeed? Models in the VS catalogue are posing provocatively and the concept is very blatantly sexualised by design. There's a lot more to VS than models in bras. There is a huge difference between VS and one's mother taking a shower or breastfeeding.
You can discreetly pick up a mag you see in a relative's house and put it behind a cushion or on a shelf and you can tell children not to intrude on others in a fitting room.
You seem to have an idea that seeing women as sex objects is something normal, and nothing can or should be be done to limit a child's exposure to that, while seeing women's bodies functioning as mammals or just going about daily life, bathing, dressing, etc., is something likely to be traumatic or to have long term negative effects.
Speaking personally, I was not stark naked while giving birth, and nor did anything shoot out of me but they have seen pictures of women giving birth as we talked and read books about the process. They have all breastfed and have all seen me breastfeeding. The older ones all changed their fair share of nappies and helped with burping. They have also been aware that I experienced morning sickness, and was sore and stiff after delivery. DD1 had DS and DD2 to see breastfeeding, by the time she was 5 years old; when DD3 was born she was 8, and 11 when DD4 was born. DS was 5 when DD4 was born and 8 when DD4 arrived and he saw me breastfeeding too. DD1, DS and DD2 all remember visiting me in the hospital a few times and all were treated to the sight of me breastfeeding babies over the years. DD3 saw less. It is unavoidable if you live in a smallish house and have a largish family.
It wasn't my personal choice to have the DCs there for the duration as they would have needed supervision, feeding, watering, bathroom, entertainment, somewhere to rest or sleep, etc., and I think it would have been very boring for them (went on for hours and hours). Fwiw, I also discouraged the DCs from walking in on me in the bathroom from about age 4/5 on as I like my privacy there, and I wanted to give them the idea that they too were entitled to their own physical privacy; everyone knocked on the bathroom door in my family from that age on and did not come in if they were told to stay out. But I would prefer my children to see me giving birth to being exposed to Page Three, VS, or the steady diet of softish porn or Nudge Nudge Wink Wink stuff that seeps into the lives of a lot of children.