Most importantly, do not buy a house now unless you are confident that it is a house you will be happy with until the kids are grown and living independently (a very long time, since you are discussing having more children). While some whole areas may have bottomed (Temecula, for instance), and the lowest-end housing in many areas may have bottomed, the kind of house you will be looking for, in the areas you would look for it, are most likely to continue down for 1-2 years, and stay low for years after that. The only thing that would prevent this from being true would be government intervention on a scale dwarfing everything seen to date, in which case everybody, everywhere will be in trouble. If you are happy where you are today, there is no urgency to buy.
If you do buy now, think long and hard about how much to put down, as this money will be immediately at risk.
If you decide to be a landlord of small properties, buy locally. Distance makes everything harder, and prevents proper oversight of both tenants and property managers.
Your circumstances are better than most, so you have options others would not have. You have a serendipitous financial gain due to the real estate bubble from the sale of your former house. If you now face the prospect of a similar loss from the bursting of the real estate bubble, what is your net? Somewhere near even, I would say.
First, decide to sell the Tempe property for whatever it will bring.
Second, come to conclusion on the value of having a high credit rating. The negative effect does not last forever. And, you will have substantial resources, even after any loss is taken (if you do not put all your money in a new house).
Third, decide whether to avail yourselves of the benefits of any Arizona non-recourse laws (whose applicability is to be confirmed). These laws were enacted specifically to protect people from being taken advantage of by the highly organized real estate industry.
After all the preceding is settled, you will have a clearer view of the factors which bear on your highly personal decision about more children, and the relative importance of the income from working versus the additional time you could spend on family matters.
