Exercise DVD for 11 year old?

[ILovedThe90s]

Since DS (11) has started secondary school, he has put on a LOT of weight. We have talked to him about it, we have argued with him about it, we have asked him to make healthy food choices when we aren't around him, we have cancelled his canteen account and provided packed lunches. He walks and buses to school, he does karate twice a week, trampolining once a week and scouts. He loves his scooter and going to the skate park, if it wasn't winter he'd be up there after school.

I have taken him to the GP about it, she said he's too young to diet, that he'll lose weight when he goes through puberty, and instead referred him for counselling for low self esteem. I took him back a second time in case there is an underlying health problem, he does have blood in his urine and no infection so she's referring him to a paediatrician. She called him back a third time to check his BP, which is ok.

He weighs 55kg and is 4 ft ?7. I weigh 58kg, and I'm just so worried about him. He got so much bigger over Christmas, even though he spent most days at the skate park for 4 hour periods.

I have an 8 yo and 3 yo as well so can't take him out for a run.

What exercise DVD would you recommend I can do with him at home?