If I were you, I'd develop them separately. Bring two developing tanks. If you can't do that, start with the Pan-F since its latent image stability is not as good as Delta. But seriously, with such a wide variation in dev time needed, you are either severely compromising one of the films, or worse yet - both. You could ruin all of the hard work you put into the shooting.
The lesson learned here is probably that it's better to shoot the same film on both occasions.