I was wondering how the two choices below differ in meaning and whether they are both idiomatic here:
Sam) I can't make it to your house today Randy; I'm sorry. But I promise to come tomorrow instead.
Randy) Well, just why?!
a. I have guests today.
b. I have guests over today.
I have an intuition that when we say: "I have a guest / some guests over" it means they have not arrived yet, and I am waiting for their arrival or expect they come soon, while when we say "I have guests," it means my guests are at my place right now. This is why I think despite the intention is clear by both options below and you may confirm that they are both idiomaticaly correct here, "b" is more natural.