Britney Spears says her sons, Sean Preston, seven, and Jayden James, six, hate kissing her in front of their friends because they don't think it's "cool".The 31-year-old singer admitted Sean Preston, seven, and Jayden James, six, from her marriage to Kevin Federline, don't like to kiss her in front of their friends because they don't think it's "cool".Speaking on Ryan Seacrest's KIIS-FM radio show, she said: "My sons are six and seven, so they're just now getting to the stage of where you can't kiss mommy in front of your friends and all that kind of stuff. They're getting what's cool and what's not."While Britney's sons can be embarrassed by her, the doting mother recorded new song 'Ooh La La' for the 'Smurfs 2' soundtrack because the boys are huge fans of the cartoon.She said: "The main reason why I did it was because my boys. They're obsessed with 'The Smurfs'. We've seen 'The Smurfs' movie a million, trillion times and they were told they could be in the music video."My oldest son, Preston, was right on cue every time they would tell him to do something in the video. They play themselves. But when we did the actual shoot of the video, I didn't see them. I was in hair and makeup, so later on I got to see what they actually did on camera - and it was adorable!"