Re: 3 kids
If you like the IS you might want to look at the new 3 series. Its a little bigger, especially in the rear while still being small and sporty. The IS will be totally refreshed this year too, and all new for 2013 most likely.
My main concern with the IS would be the rear facing seat, once he's out of that it might be okay...
2014 Jeep Grand Cherokee Overland V6 4X4. Maximum Steel w/ Vesuvio Jeep Brown/Indigo Blue. Advanced Tech Pkg.
2013 Lexus GS350 AWD, Liquid Platinum w/ Flaxen. Luxury & Cold Weather Pkg
Previous Jeep: 2011 Grand Cherokee Laredo X w/Nav, QT1 & Trailer Tow