Indianapolis and Kansas City are about 452 miles apart by road. Split the difference and you arrive near Chicago, the city closest to the halfway point between them. That puts roughly 3 hr 27 min of driving on the Indianapolis side and 8 hr 39 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 Chicago suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If Chicago doesn't have what you're after, Louisville and Milwaukee are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Indianapolis and Kansas City.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.