HRW's Development Department is one of the most family friendly departments that I have encountered in the nonprofit sector. From the flexible work hours, opporutnities to work from home on Fridays, and extraordinarily generous paid parental leave policies, it really doesn't get better.
I worked there for two years. While I did not have children during that time, I did think the overall benefits were good. The company environment is not very conducive to work life balance unless you are much more senior.