Your road trip should get good mileage. You'll be on the open road. Freeway driving is really good for 2nd generation Transit Connect. I've seen great mileage the few times where I was able to drive continuously at freeway speed, and cover enough miles to actually use several gallons of fuel.
It's the stop & go city driving, where you are stopped and idling, that really hurts fuel economy.
My best tank was 27.1 MPG. That was with a couple of longer trips mixed in with my daily driving.