The best strategy (I know you won't do it :-))

Move your family to a low cost area with healthy growh potential, then you can re-start your leverage game to take advantage of the first pot of gold you earned in the high cost area. With 80% Loan to value ratio, think about how much your 1200K equity can borrow: 6000K. Total 7200K you can deploy in a low-cost area, think about how many low-cost houses you can buy...

I studied those rich people in real estate:
1) Developer, then you can stay locally.
2) Go across the US to best use his equity for sequential leverage.

Other than 1) or 2), I can't think of anyother way in real estate for you to grow from 1200K to 10M quickly. Of course, you can let inflation and time to grow your Bay area properties to 10M in 10-20 years, but that's not really making money, that's simply getting even with inflation.