I would, regardless of full, partial or self care, take over the grain and hay feeding. To avoid one horse being fed, the neighbor not.
As for when, with two feedings, 12 hours in between, so 6am and again 6 pm. Hay half an hour before grain.
After horses are out, clean and bed stalls, get everything ready for evening feeding, leaving hay outside of stalls, so they still have the full ration for the night, even when they come in early due to bad weather.
Since I'd have my own horses there too, I'd actually feed 3 times, taking above hours, splitting morning feed in half and give second half at noon. For horses outside with grass or hay, only the sweetfeed/grain.
I would do additional cleaning only if horses stay in.
I also wouldn't feed so late. It's a long day already, no need to make it even longer. If days are shorter, give the bigger portions at night.