By all accounts those children raised in circumstances like long term ocean cruising seem to benefit from the experience on a number of different levels. And, probably, the adult parents will have more anxieties and issues with the whole concept than the children will.
We've tried to live by the credo "you mostly regret the things you didn't try". I've tried some offshore, but the circumstances were not good and the experience was not terribly positive. I'd try it again given a better boat, crew etc etc.
But I would not discourage such an idea, and more power to those who pull it off.
However, at the risk of proving Surf's pre-emptive attempt to still the voices of reason, I would certainly suggest buying the boat and spending a few seasons learning her habits, shortcomings, systems and needs before heading offshore. Imagine finding a serious flaw somewhere, 4 - 5 days and 500 miles offshore in the first storm.... now what?