You wrote that both employers have recently been underwater. So just exactly how secure do you feel your incomes are? If one job vanishes, how well can you make it on one income? How slow is the hiring cycle in that parent’s industry? Think through your worst-case scenario too.
How are you planning pay for your children’s educations right now? Out of current income? Or, do you have some savings available for that? If you think you can do it out of current income, then pull that money out each month starting now, slap it into savings, and live as though you already had one kid in college. This will give you a clearer reality chack about what is possible.