Thankfully your girls have a switched on mum, your positivity and love for the female body should rub off on them.
I always used to read these stupid magazines at that age, so my roll models were airbrushed fakes, not to mention my mum was a beautician and obsessed with her appearance spending hours over it to an unhealthy degree. My mum tried to wax my hairs when I will still in primary school and I hated the pain so I started shaving instead to my regret now >< I was a Tom boy too so the moment it all starts switching to the pressure when your body starts changing and u feel u have to change to fit in, is all crap. Positive roll models like urself should make all the difference, maybe you can show your girl some of the body positivity a stuff from from the Internet that the reality is women are all different and all beautiful no matter what shape or size, the belly decoration sounds ace, a bit like how women have been painting their stretch marks recently ❤️