Bologna is one of my favorite cities in Italy to indulge in culinary delights. Like mentioned above, I do not recommend going to Eataly. Save the trip to Eataly when you're back stateside (Las Vegas opens tomorrow) and missing Italy. Not a waste of time, but it feels too commercial. I'd ditch the car and stay in an airbnb around the centro storico/ghetto area just south/se of Piazza Maggiore. I booked the Tastybus food tour out of Parma (45 min by train) to tour parmigiano reggiano, parma ham, and balsamic vinegar production facilities. Was a bit reserved about a "tour" but I highly recommended it and you get to see some beautiful scenery! It's the real deal.
A couple of my favorites...
Salumeria Simoni- "Tortellino di pane" Crescent shaped sandwich stuffed with mortadella (focaccia dough?).
Caffe Terzi- Best coffee I've ever had. Ask for the special menu (book). Stand at the counter to see the magic happen.
Many, many al fresco restaurants just off the piazza. Most are open until 23:30 which is nice for late dinners or jet laggers.
Enjoy! I may see you there since AA is flying direct next summer! What a treat!