Ask HN: What am I missing?

Summary: Need HN's help in thinking through a real dilemma.

A hacker by profession, I currently work for a popular startup in the valley, on track for IPO in early 2014. I joined very early (5th, 400 now). I'm however now all set to go on my own. I've found a great co-founder who already has some traction in the space that's dear to me.

Having gotten the wind though, my employer has come back with a very lucrative offer. It's loaded with dough, a shiny "Director" title, responsibility of multiple teams and enough autonomy, with a moral commitment of staying until the IPO. Very flattering and humbling.

It's getting harder by the day to decline the offer. Need HN's help to think this through.

Reasons for taking the offer: 1) Dough. ~200K salary + 7 digit-options of a fast-growing pre-ipo company. 2) New title opens up a lot of possibilities. e.g. VP at another fast-growing startup. 3) Staying thru an IPO from the beginning likely doesn't happen often in a lifetime.

Things I'd lose if I stayed until 2014: 1) The awesome co-founder 2) (likely) Currently favorable economy 3) Some itch. I'll be 36 by then

What else am I missing? This is of-course a personal decision, but I'll really appreciate any words of wisdom.

Me: 33 M, a husband, a son, a father of a priceless 2 year old, with 2nd one in the pipeline. Busy enough to not do a startup part-time. Monetarily quite comfortable, but not financially independent. Not keen on buying a house anytime soon.