I have always had a couple of toys for kids that age. A 4 piece puzzle, a drag toy, a cardboard book, and paper and large crayons. You never know! But the mom does. If the child falls in love with something, I let him take it home. Otherwise, I just sterilize it and wait for the next kid.
As far as dinnerware, you can manage. I always have had a sippy cup and Cheerios around, just in case. I grew up on phone books and towels, but it seems most parents bring their own dining chair friendly booster now. Great!
For the food, a few kid friendly foods are good: plain chicken nuggets, crackers from the baby section, but any child that age should be able to handle adult food that the parent can rinse off and cut into chunks. Offer fruit that you have around, if needed, and let the parent serve it
. For example, some kids need grapes cut in half, some are fine with a whole grape. For bananas, some want quarter slices, some a whole slice 1/4 in thick!
You seem to have done a great job of toddler-proofing the home and are aware of the unforeseen dangers. Mom should be, too.
Lots of plastic bags and spray cleaners are your friend, too.
Not saying anything in particular here......Most of us have that on hand anyway.