My son could do that no bother on his BMX. He's 11.
Bring him along. Does he like his teeth? Being fair to me it's not quite as easy as the camera makes it look, the run up is short, the lip is off-putting, the landing is concrete covered in moss, slippery plastic and swings. The reason I cocked up the small one was in part due to the fact that on accelerating for it I wheelspan on the plastic but I'd committed myself at that point so went for it anyway with clenched buttocks.
GEDA – correct, the seatpost height didn't help but I don't think it was the main issue here, lack of speed and poor technique set me up all wrong for the little one and the bigger one is even harder to get set up for so it's going to take a bit more persuasion on my part. But I promise to keep you updated on my poor progress as soon as my new seatpost arrives 🙂