&gt;  if you can make the decision to own a sex toy, surely you can make the decision to have sex?

There is absolutely no correlation between those two statements.

&gt; As a collective society we have decided that that is not okay, as displayed by age restrictions on these products and the age of consent.

Collective society has decided a lot of questionable stuff in the past. It's ad populum, hence it is wrong.

&gt; but that is because we, as a society, have decided that that age is appropriate for people to start playing around with toys and sex.

Ad populum once again. Why is it fine for kids to fiddle with their genitalia with whatever they find in their viscinity instead of something that was designed for that purpose?

&gt; it's actually really interesting how sexualised culture has become in recent years

Human culture was always extremely sexualized. One of the first works of arts featured a lot of sexual imagery and it never changed for being more prude, except when churches decided it was bad all of a sudden.

&gt; However, children under 16 e.g. 12 year olds should be allowed to retain their ability to be kids

You are wording it in the way as if I was shoving dildos into teenagers. Nobody is taking their ability from them. They don't magically turn into adults the moment they find out what sexual stimulation is. Stop bombarding me with things that have no logical correlation whatsoever.

&gt; honestly think it's detrimental to children's mental health to believe they're in some kind of "weird" minority that aren't sexually active, when in reality 95% of twelve year olds aren't.

They don't masturbate because they think they are in minority, they do that because it's what their bodies crave for. This is literally the point of puberty.

&gt;  However, I feel that promoting that kind of behaviour is something so be discouraged for fear of normalising it and pressuring others into becoming sexually active before they are ready to.

Am I promoting that teenagers should all use sex toys? No. Am I saying that parents should buy sex toys for their kids for Christmas? No. I am saying that if a teenager chooses to have a sex toy we should not demonize them as a some sort of deluded, mentally ill sex fiend.