There is also Conner Prairie in NE Indy Metro Area (Fishers, IN).
The Monuments downtown are something to see as well, as Indy has the 2nd largest amount of war memorials of any city in the US (2nd only to DC of course).
Circle Center Mall is fun if your kids like shopping.
There are two laser tag places in Indy area, which are really great (Laser Flash in Carmel being the larger).
The Zoo is pretty big and then there is the Indiana State Museum with tons of stuff for kids to do, Interactive things as the museum is darn new.
Well, and if you/your kids like ghost tours, of course there is the year round ghost tour company unseenpress.com, Inc. - Historic Indiana Ghost Walks and Tours.
And there is a Holiday Inn hotel on I465 North side on Michigan which has a Water Park.