Austin and Kansas City are about 636 miles apart by road. Split the difference and you arrive near Oklahoma City, the city closest to the halfway point between them. That puts roughly 7 hr 32 min of driving on the Austin side and 6 hr 15 min on the Kansas City side — the fairest single meeting point among the cities near the middle.
That's a half-day drive from each side, so Oklahoma City suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If Oklahoma City doesn't have what you're after, Dallas and Houston are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Austin and Kansas City.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.