You and your family are invited.
That is grammatically correct.
All staff are invited would be considered correct in English usage. American usage may be different.
"You are most welcome" is correct grammar.
It is correct to say that you are invited to a particular event, not invited for.
No, the correct grammar is "you and Bob." Using "and" helps to combine the two entities into a single unit, emphasizing that both "you" and "Bob" are part of the same group.
No, "will be had" is not a correct grammar. The correct grammar would be "will have."
Yes it is.
The correct form of invitation in "you are invited to lunch" or "you are invited at lunch" is "you are invited to lunch". You could also say, "you are invited to lunch at my house" as this would be grammatically correct.
No, it is correct grammar, not a correct grammar.
"On a train" is correct grammar.
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