Here I am thinking that leaving an SUV for a Model S might be difficult with my wife and 2 small kids, and you're planning to haul 5 kids and 2 adults around in one?
How will you possibly have enough cargo space to bring your family anywhere? I'm pretty sure there's no tandem stroller for your twins that will fit in the frunk with diaper bags and all of the other accessories that come along with children. Putting cargo in the rear with kids in the jump seats would be a huge safety concern for me.
Those rear-facing seats are meant for occasional use, as evidenced by the lack of proper climate control, and a lack of physical controls for anything except opening the hatch in an emergency. It's your life and your decision, but unless you want to double your budget for a Model X, you may want to consider true 7-passenger vehicles from brands besides Tesla. If you're firm on spending $35K, opening your search will provide you with other vehicle options that are more suited for you and your growing family.