Chicago is home to the Chicago Bears (football), the Chicago Bulls (basketball) and the Chicago Cubs (baseball). The Bears play at Soldier Field, the Bulls at W Madison St and the Cubs at Wrigley Park. All venues are easily accessible from downtown Chicago on public transport and all are family friendly.
It is very hard to get Bears tickets and they start at around $100 if you are lucky enough to get one at face value. There is a thriving secondary market but it is pricy! The Bears website is the best place for information on tickets
http://www.chicagobears.com/tickets-and-stadium/individual-game-tickets.html
It is easier to get to a Bulls game but again these sell out quickly. Their website is the best place to go for information.
Cubs tickets are very easy to come by – the major league baseball teams play so many games that even the most die-hard fans would struggle to get to all of them. I personally love a baseball game. Wrigley Park is a Chicago institution and sitting in the afternoon sunshine with a beer is very relaxing although I spend more time people watching than watching the game. Tickets start at around $20 for a mid week game and go up from there. The Cubs website is the best place to go to buy tickets