I'm pretty sure that children's toothpastes don't have flouride, which make them quite useless. The main active ingredient in toothpaste is Flouride. Honestly, I feel this is overblown. Heavy metals are already in everything we eat (rice, chocolate, tea), what matters is that you don't consume too much of them. Brushing twice per day isn't going to get you a life-threatening dose of heavy metals, but, on the other hand, not brushing well can lead to bad oral health which can kill.
I'm pretty sure you can get a Thinkpad with Linux preloaded, and they are great laptops for Linux too which is a plus, but they are quite expensive.