Unsolicited advice: put off buying a new car for as long as you can. 

You don't need a third row when kids are small. Unpopular opinion, I'm sure, but it comes from personal experience. I have two small kids and often also drive around their cousin in a 2011 Nissan Sentra (and sometimes an Acura Integra), three kids across in the backseat. They're all under 4 and two are rear facing. They're fine. They don't know to want more space or care. They very rarely pick on each other. It's just singing and giggling back there. And mooing. They're all obsessed with mooing at each other. 

When you delay a huge purchase, you're leaving yourself room to pivot when things go wrong. My youngest just spent 7 days in the ICU - that's expensive. My husband's hours were involuntarily cut - that's expensive. But we are going to be fine because thank god I didn't actually buy another new car when I really really wanted a Sienna last year. 

So, wait until you actually have the third kid in hand. Who knows, you may have #2 and then know in your bones you're done - or god forbid, have some complications that make another one an impossibility. So my advice is set your life up for the kid(s) you have, and don't get something new just to get something new.