Some Advice please - been a while

Getting back into Photography after about 6 years, and looking for a bit of advice. The thing that has kick started me again is the fact that we are going to Norway in Feb, to (hopefully) see Northern Lights; together with the fact that I am retiring and have more time to devote.
I was always a Canon user, and previously had 350, 450 etc., but now looking to go to a next level. Budget wise I'm looking to spend around £1,200 - £1,500 for a camera and lens, preferably wide enough to handle landscapes and N Lights if they appear.
Was looking at the 6D Mk2 - which is a bit over my budget, then looking at the 80D it seems that this is almost as full featured for a lot less.
There is a bundle available of the 80D with an 18mm - 55mm and 55mm - 250mm IS STM lenses, (plus bag, tripod) for £1215 ...and a similar bundle of 80D plus the 18mm - 135mm IS USM lens for £1271
The questions are; would 18mm be wide enough for my needs?
Would I be better with the 1 lens 18-135 USM rather than the 2 STMs ..even though a few bob more?
Any other advice very much appreciated.
Phil
I was always a Canon user, and previously had 350, 450 etc., but now looking to go to a next level. Budget wise I'm looking to spend around £1,200 - £1,500 for a camera and lens, preferably wide enough to handle landscapes and N Lights if they appear.
Was looking at the 6D Mk2 - which is a bit over my budget, then looking at the 80D it seems that this is almost as full featured for a lot less.
There is a bundle available of the 80D with an 18mm - 55mm and 55mm - 250mm IS STM lenses, (plus bag, tripod) for £1215 ...and a similar bundle of 80D plus the 18mm - 135mm IS USM lens for £1271
The questions are; would 18mm be wide enough for my needs?
Would I be better with the 1 lens 18-135 USM rather than the 2 STMs ..even though a few bob more?
Any other advice very much appreciated.
Phil

I am not an expert in the type of camera or lens which is best. I used a Sony 850 DSLR and a Tamron 28-300. I was on a ship, which was moving, so tripod was not actually a help. Fast shutter means that the images were very dark and Adobe Camera Raw was indispensable. They are not moving quickly but do move continuously and I think Jack's suggestion of long shutter may get blurry images ( I would hazard a guess that the speed is 'normal walking speed'). The Sony is a very noisy camera so increasing the ISO too much is not really an option for anything. If you are land based then it becomes a little simpler. I hope you get to see them - quite an experience.

Sometimes you will put a lens on a tripod, and instead of silence, especially on Canon lenses you will hear a quiet whooshing sound that tells you the IS is busy.
I kept the IS turned on with a Sigma 17;to 50 for architecture, and everything was just vaguely unsharpened, as if a really poor lens had been used. It wasn't obvious on the camera back, but needed a reshoot.
I kept the IS turned on with a Sigma 17;to 50 for architecture, and everything was just vaguely unsharpened, as if a really poor lens had been used. It wasn't obvious on the camera back, but needed a reshoot.