Hey Buffy,
To be honest, I think you can go wherever you like as long as you give her a good bit of time beforehand to suss out her surrounding and get settled in.
After much trial and error my girls get on with it in their own muddy arks in their pens with no rails, lights or really me involved at all. They seem happy with this and actually we only loose the odd one to squishing. Farrowed in mid Jan last year and everyone was toasty warm with mum.
However, I don't have a lovely set up like you do available so I can't compare. If you want to get hands on, or if the sow is inexperienced, then definitely make it as easy and safe for yourself as possible. Arks are very tiny when you're all in there!
I do have a friend who lost a whole litter to an unknown predator, possibly fox? So take Into account where you are and what threats you might encounter.