trying to get seller to cancel winning bid that our autistic son managed to win

[craig3272]

Our Autistic son put a bid on an item which we were unaware of until contacted by ebay to say we had won. it is a hot wheels car. The postage is very high which put us off. We contacted the seller and explained we didn't know about the item until it was too late and the fact it was done by our autistic son who also has an intellectual disability. (we allow him to put things on watch, but somehow he has managed to put a maximum bid of $490 on it as well) We contacted ebay to also explain. The seller has now told us too bad, we should have known the postage was going to be high on our item. ebay have informed us we had to ask the seller to cancel (obviously he won't) then if that fails we have to wait until the seller puts us on the bad buyers list. Any ideas please?