Flight
Chicago has two airports: O'Hare will be the easiest for you to fly into, but for those coming from AZ, Midway will be your destination if flying SouthWest. Both are equidistant to the city, so easy to fly in to either.
House Or Rental
Airbnb or VRBO are great options for groups that want a kitchen and the comfort of "home." There are a some good options for houses that would accommodate 6+ people and many that would accommodate fewer. If you don't have a car, West Town can be a bit of a hike to any public transportation, so anticipate lyfting or ubering around or walking 15 or so minutes to the trains. Another option is staying in the loop, where public transport abounds and will be closer to touristy things such as Michigan Ave, Navy Pier, museums etc... Neighborhoods to look into: The Loop, Fulton Market, West Loop, West Town, Lincoln Park, South Loop, Gold Coast
Hotel
There are hundreds of hotels to choose from in Chicago - and many that are in all the same neighborhoods that we mentioned in the Airbnb section. Some great options: The Wit, Palmer House, River Hotel, Club Quarters, Hyatt Centric etc...