I think your body should still be treated with respect after you die, but everyone should be given the choice of a donor card and maybe their kids/parents should be too, 'cause they're kind of close to you.
As for 'owning' your body... do you even own it when you're alive? It's not really a possession, but kind of 'you'.... I'd say you 'are' your body, but I don't know about owning... it's a confusing expression ^^"