This looks fantastic. Seriously, really good.
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.