The dictionary definition of "itinerary" is:
A route or proposed route of a journey.
That's essentially the same as the definition you found.
I have never heard someone use the word "itinerary" to mean the schedule of an event -- unless, of course, the "event" is a trip of some sort.
You certainly COULD use it to describe the schedule of an event as a metaphor of some kind. Like, "At this conference, we will be visiting many fields of science. The first stop on our itinerary is Chemistry. The second stop is Physics ..." etc. If the event is related to travel, like if it's a convention of travel agents, that might be clever and cute. But "cute" tends to get tiring after a while, so I'd be cautious about doing this.