Well good news for you is the weather should be decent enough to spend time outside, and summer in the city can be pretty amazing.
Assuming you’ll be in the downtown/ north of downtown area I’d plan on spending some time around the lakefront where you’ll find a ton of activity on the beaches and bike paths. Check and see if the Cubs are in town for that classic experience (skip the white Sox), and the architectural river tour is another thing worth doing. Depending on your timing there might be a good music fest in Grant Park, concert at Soldiers Field or Wrigley, or neighborhood block party going on. And of course there are the obligatory museums and shopping. The museum of contemporary art (vs the Art Institute) is very underrated, near the Michigan Avenue shops and can be done in an hour or so.
For food it depends what you are into. The classic Chicago stuff is the healthy trio of deep dish pizza, beef sandwiches (almost any place will do a solid effort you don’t go where the Bear is filmed) and Chicago style hot dogs - wiener circle is the quintessential spot. For finer dining it really depends what you are after but you’ll find plenty of options in the west loop on Randolph, and the Publican is one place I always recommend. If there is a particular type of food you want I can post more names.
I’m way too old to go to bars anymore so if you are looking for clubs I have no idea what is cool but there are no shortage of places to go drinking.