I suppose some states may have different regulations effecting the system, but every plan I've ever seen doesn't differentiate based on the number of dependents you have. Rates are effectively tiered to single, married, or family.
This varies significantly from state-to-state, by insurer, and even by plan. In places that do price based on actually composition for family plans, there's rarely a particularly linear correlation between family size and rates. (Also, good luck getting an insurer to tell you your actual rate on an online tool :/)
I'd love to be able to specify the number of children I'd be putting on my plan (maybe not on that first page, but on an internal "refine" page?).
Also, it'd be great to have checkboxes allowing me to select two or three plans, to then compare them head-to-head.
But, again, this is an excellent first version. I look forward to seeing where it goes.