Northern Lights - 14-24 F2.8 or 16-35 F4 or wait ?

I am on process planning to go to North of Europe for watching Northern Lights next year

today I have a 24-70 F2.8 fitting on a D3s and 70-200 VRII

My questions are:

- which lenses did I need to get benefit of Northern Lights in an optimal condition?

- If I have to buy a more wider zoom lense, which one to select and why?

- If a fix Wide Angle is better, please tell me which one to take and why?

Thanks

Philippe