To talk about several people each doing the same thing, English
usually prefers a plural noun for the repeated idea.
Tell the kids to bring raincoats to school tomorrow.
(More natural than Tell the kids to bring a raincoat ...)
Plural forms are almost always used in this case if here are
Tell the children to blow their noses. (NOT ... to blow their nose.)
Six people lost their lives in the accident.
Michael Swan (2005.530), Practical English Usage.
However, for an activity done together, the singular form is natural. Compare:
When I was working, my wife and I had (our) breakfast together.
Now that I am retired, she has left for work before I get up, so we have our breakfasts separately.
If your cats had separate plates, I would use the plural form. If they ate from one plate, I think both singular and plural are possible. We can think of each cat having its own breakfast - two cats, two breakfasts - or of the two cats sharing a singular meal together.