Here is a killer 10 minute ab workout for long, lean defined abs.  You don't need any equipment just the will to do it!  I carried four babies and while I had a history of being pretty fit I also did two years of bed rest for babies #3 & #4.  Anything is possible, and you don't need washboard abs to find true happiness.  A strong core never hurts though and will keep your back healthy as you get older and while you chase around those kiddos.
30 seconds on/30 off.  Little stretch at the end so if you do it twice then stretch at the very end only.  Get it!  I'll do it if you do it!