There will be various parental controls and a Kids Store where free and paid apps can be "purchased". Any paid app is going to require the PIN number to be punched in after being selected. The Kids Mode will have a cartoon guide named Kroko that will take you through the task of selecting a PIN number.
Those who have seen the Kids Mode describe it as being colorful and flat, a description that is supposed to cover all of Sammy's apps on the new iteration of its UI. Of course, more will be made known next week at MWC. In the meantime, you can get your kids excited by telling them all about it.
source: SamMobile via GSMArena