"The guests do not eat lunch."
Translation:Die Gäste essen kein Mittagessen.
Could you please provide the exact phrases you mean? I guess you mean something like: "Die Gäste essen nicht zu Mittag." or something?
You can say:
"ich esse Mittag" - "I eat lunch"
"ich esse zu Mittag" - equivalent to "I eat at lunch time (and I do it)."
"ich bin zu Mittag" - "I am out for lunch" or "I am at lunch"
All three are meaning the same.