I found that the problem with my mother's boredom was that it was internal and there wasn't much I could do to engage her attention. She did respond well to animals so if you have a pet, that could help. If not, perhaps walks in the park where you can see animals might work. We would take my mother to a dog park and she seemed to enjoy that.
Music seems to work well for a lot of people.
As for the food, yes, small but frequent offerings are good for people who have small appetites. My mother eats like a shark still (in the late stages of AD) so I have never had had to deal with that and hope I never will.
I would also focus on calories and treats now and not be too rigid about what was being offered.