I would think "Guests have arrived!" would also be a valid translation.
Or "The guests have arrived!"
If it were "Guests have arrived," denoting an indeterminate or indefinite quantity, it would likely be introduced with existential "有" (有客人到了).
stupid question but I'm really confused about the differences between 到 and 来
到 is to arrive in a literal or abstract sense
来 is to come, the opposite of 去