Good Grief! If Donkeys are like minis, she has DROPPED and is ready to pop soon.
I think you've covered most of the bases..... Make sure she delivers inside and on a nice thick bedded stall with heat lamps, lots of drying towels, and a baby blanket ready.....
I'd probably not let mom and baby outside for over 24 hours, and then only if the weather was above freezing -- with the baby wearing the blanket. And time outside would probably be limitted.
The foaling stall bedding should probably be totally replaced and thickly bedded again because mom and baby will be spending more time in there than they would if it were a Spring or Summer birth.
Other than all that, there's not much more you can do! Just use your own judgement on when and how long they should be outside for the first couple of weeks.....
I'm sure other folks will have more suggestions.....
MA