One thought ... you've been successful trading part time. But you also have the security of your salary, bonus and other perks (like health insurance) to fall back on if you started to lose $$ trading. Relying on trading profits to support a family of 4 may be a bigger challenge than you realize. If I were you I'd only consider going FT after I had paid off my mortgage, credit card debt (if any) and any car loans. You don't need the pressure early on of being in a "must make" money from day one. I'd also make sure my trading funds were at least $400K if you're trading retail. I went through a similar scenario back in 1996 except I didn't have any kids. I gave up a lot (corp. job, income, bonus, benefits) and had a few challenges along the way and not only survived but am trading as well as ever today. For me the key was getting through the tough times and adapting to the markets and feeling you can make money in any market. I don't think you can put a price tag on the freedom trading allows you.
Absolutley do not change a thing. If your trading works during the limited time that you have available then stick with it. Increasing exposure to varying markets may not work for your style.
Quit and trade fulltime everyone on here is absolutely killing it. You'd be crazy not to give everything away and take a punt. Think of the kids and what you can offer them.
"Independence is the only gauge of human virtue and value. What a man is and makes of himself; not what he has or hasn't done for others. There is no substitute for personal dignity" Ayn Rand, The Fountainhead, 1943. Hey it is your life. You plan it as you see fit. If you think you can do it go for it. If your plan A does not work, execute plan B!
Problem is I can't work FT and trade FT. Work interferes with trading and visa/versa. My most productive trading hours are morning and that's also when the most demands are placed on me at work. Thanks for you comment though.
Put $250k each in a trust for the kids so they have a shot at college (you owe them a fair shot at life. if you take that away they *will* hate you for it.) Then build family spending reserves for a year. Then seed your personal trading fund. Then quit.
A couple of comments have been made along this line. "Why change a good thing". Very true. But thinking about reaching for my dreams.