Yes, the double negative is easy to miss. It translated to "I hope there is nothing but cabbage for dinner" in my head. It would have been simpler if they'd put "J'espère qu'il y a plus que du chou pour le dîner". But it's a good lesson to us as is. ;-)
Agreed, it works better and is less clumsy. It's also what you get if you use Reverso - although Collins returns: I hope there is more to it than cabbage for dinner. Perhaps it's just a matter of one's taste for brassicas!