No doubt everyone else has thought this already and been too polite to crack the obvious joke, but I can't help feeling that the phrase "a G&T child" ought to mean "one who gives their parents a strong need for a stiff drink on a regular basis". (Come to think of it, mine did drink a lot of G&Ts...)

It's difficult to know everything my parents did that worked, because I suspect they provided a lot of important support around age 2-3 (round about when I was learning to read) that I don't remember clearly. Mum has mentioned that there was some kind of child psychologist specialist who was giving them advice, and of whom she speaks highly in retrospect, but I remember nothing of him except his name.

What I can remember is that they were happy to fill the house with computers from (my) age five and tolerant of me playing with them at all hours (and, similarly to what resonant suggests above, they didn't try to impose particular goals on that activity but let me just noodle around doing my own thing at my own pace), and when it became clear that my local primary school was boring me to tears with its slow pace they moved me to a school filled with other gifted kids which worked much better for me, and then sent me to secondary school a year ahead.

(widgetfox mentions the risk of social problems if moved up a year due to not having so much in common with your classmates. I certainly did have some of that, but I'd say that in my case it wasn't enough to have made it a bad idea.)