Quality food containers. I'd go with Glass for formula/milk bottles even. Unless it's going straight from the source 100% of the time. Remember "BPA free" mostly means they are using BPA (version 2.0) and it's just as bad or worse in many cases. When you get to sippy cups they try to eat them. It always seems odd to buy organic, non-gmo, free ranged, blah blah, food, but then let the kids eat plastics from 3rd world countries. That's a ways out though.
I'd get some type of rear seating area covers to go down under the kids seats that keep everything out of the cracks in the seats. Or just wrap the rear seats in a tarp
Not that you're going to let junior eat in the car or anything