Advice for first time visit in September?

Hello all!

My mom and I are visiting Chicago for a week for the first time the second week of September and I'm hoping to get some advice and suggestions.

We are looking at getting the City Pass because we are big museum people, but we weren't sure with what those places cost regularly if the pass is worth it or if it's too restrictive.

We're staying in at a hotel towards the top of the magnificent mile area, to my understanding it's close to public transportation (please correct me if I'm mistaken). Where we live does not have widely available public transportation, however we're used to navigating the metro in Montreal and Subway in Boston and NYC. We are wondering if the system in Chicago is similar to navigate as far as safety and understanding routes. We're hoping to mainly walk and uses public transportation and avoid ride share/taxis as much as possible.

Id love any suggestions on must see or do things, or places to eat for a first visit with a week stay. We're not dead set on anything in particular (except the Obama presidential center which we already have tickets for).

I've been looking everywhere online and plan to dig into this thread more now that I've found it.

Thanks in advance if anyone is able to help!