7:00 is a safe estimate. I assume you're taking the 'L' to get from O'Hare to your hotel? That ride will be about an hour and 20 minutes. I also imagine you'll want to do as little walking as possible with your luggage, so you'll want to take a route that include a bus stop near your hotel. (Google Maps will also give you an option of getting off at LaSalle, but that includes walking for about half a mile.) I don't remember what hotel you're staying at, but I looked up directions to the Hilton Chicago since you said it's nearby:
Chicago O'Hare International Airport, Chicago, IL 60666 to Hertz Local Edition - Hilton Chicago - Google Maps
Ono and I won't be available between 7 and 10, but there are plenty of food options near your hotel. If you're feeling tired from the flight and want to get the closest thing - and also just can't wait to try Chicago style pizza - there's a
Lou Malnati's only
a couple blocks away. (Again, directions are from Hilton Chicago, but you can change that.) Alternatively, if you'd like to wait on the Chicago style pizza and go for something
equally nearby but even less healthy, there's the famous
Harold's Chicken Shack (
Presidentially endorsed!

).
If you're willing to travel more than a few blocks right after you get here, there are obviously a ton more options. Too many to list, in fact

.
Xoco is a relatively new and relatively inexpensive Mexican restaurant from Rick Bayless, and totally worth the wait in line if you're up to it (I'd estimate probably half an hour wait). It's a
short train ride away, or you can
walk the 1.5mi and see the city.
The Berghoff is Chicago's oldest restaurant (with Chicago's very first post-prohibition liquor license!) and it used to be a great place for relatively authentic German food, but I haven't been there since it changed ownership. It's a
15 minute walk or
10 minute bus ride away.
The Billy Goat Tavern is another Chicago institution with some wonderfully unhealthy food. If you believe the legend, it's founder and his pet goat are responsible for the Cubs sucking the past 65 years and it was the inspiration for Jim Belushi's "Cheezborger! Cheezborger!" sketch on SNL (whether or not that's actually true, they've embraced it). It's a little over a mile away, so you can
walk and see the city or
take the bus for a shorter trip (note, it's located on the
lower level of Michigan Avenue). Since you don't want to go to the place that
Anthony Bourdain says has
the best Chicago hot dogs (and I thought you cared about good food

), you could settle for
Portillo's on Friday night. Again, a
short train ride or
longer walk away. Anyway, I'll stop there, but there are plenty of other places too!
Side note: You mentioned that someone told you you have to go to Walker Brother's? It just occurred to me that the only locations are in the suburbs. The good news is that the one closest to Chicago is also not very far from the Linden stop, which is where you'd get off to go to Baha'i Temple (
map). Something to consider if you really want to go there. I'm not a huge pancake fan, so I can't really tell you if it's worth it or not.