As everyone has said, "to be invited" is correct.
The basic sentence structure is: It's + adj./noun ... to + verb.
It's an honor to be here. (It's + noun...)
It's great to see you. (It's + adjective)
It's a pleasure to meet you. (It's + noun)
Is it OK to call you "John"? (question form)
In this case, it's a little complicated because the sentence is passive. So the structure is: It's + adj./noun + to be + past participle
It's an honor to be invited...
It's annoying to be called in the middle of the night.
It's embarrassing to be treated that way.
There are other variations of this structure. Just remember that sentences beginning with It's + adj. or It's + noun need "to" before the verb.