I'd say- Solarbeam on ninetales. when it's sent in it will probably set the sun up, I think solarbeam is a good choice. Energy ball does work if you see LOTS of other weather teams. if you don't- just stick with solarbeam.
On magmortar, I think HP grass would be better because if you're up against a Pokemon and your sun setters are dead, you wouldn't be able to use solarbeam so I think HP grass would be best!
Hope I helped! :3