I have a party in which 3/5 of them are semi-regularly recieving visions or dreams, visitations from the gods and fates and so forth.

I have a dream I wish to present to two of them which will be akin to the memory scenes in Harry Potter & the Chamber of Secrets, where they are witnesses of the memory, rather than interacting with it. My current thoughts are:

1: Roleplay it with myself. Basically act it out to them, describing it aloud. I am hesitant to do so, as it may be quite long.

2: Write it as a short story for them to read. This would work well, but is perhaps impersonal and also lets them re-read it, giving them perfect knowledge of it.

I don't know how else I could go about it. Has anyone ever had a good plan for delivering exposition like this? The dream will be a discussion between dragons, on what they should do in response to a threat. I am unsure of the best approach!

Well, I perfer to give my players 'character info' in text messages, and in one of these I described a dream where the mindflayers were communicating with said player.

You could also do a mix of both, roleplay what they see in the vision, describe the dragons discussing among themselves, perhaps even making voices for the introduction

And then hand them out a script of the exchange so they can read the rest of the exchange so it can save time and effort. 

You could write it, and leave stuff out. Tell them it’s how they remember the dream, and we all remember dreams imperfectly. 
Then you can include the stuff that really matters, and leave gaps. And make them deliberate and obvious “the next part of your dream is hard to recall, you remember the color blue and the letter R.”

Then, any time they see something blue or meet someone with an R name they’ll wonder if it’s from the dream. It will drive them nuts, hopefully in a good way.

I'm an online DM, so I can easily just write up the visions and post them in private channels for players to read during a long rest or between sessions. If the scenes don't involve any interaction, though, I usually try to keep them short or just summarize dialogue. 

You might consider giving the scene to the players piecemeal. Maybe hearing a certain word/phrase or seeing a visual cue triggers a flashback vision of a portion of the conversation that contained the trigger stimulus. You can even be sneaky and give the scene segments to your players out of order. A puzzle for them to solve.

If it were me, I'd give the two PCs different parts of the memory that only make complete sense if they share intel with each other. That way you share the burden of the lore dump, and still allow the players to interact with what they find, at least once they come to.

Quote from theologyofbagels >>

I'm an online DM, so I can easily just write up the visions and post them in private channels for players to read during a long rest or between sessions. If the scenes don't involve any interaction, though, I usually try to keep them short or just summarize dialogue. 

You might consider giving the scene to the players piecemeal. Maybe hearing a certain word/phrase or seeing a visual cue triggers a flashback vision of a portion of the conversation that contained the trigger stimulus. You can even be sneaky and give the scene segments to your players out of order. A puzzle for them to solve.

If it were me, I'd give the two PCs different parts of the memory that only make complete sense if they share intel with each other. That way you share the burden of the lore dump, and still allow the players to interact with what they find, at least once they come to.

Now that is a wonderful approach, I may use that in the future. For now, I want the message to be quite clear, as it's a direct information dump from a god, but making them collaborate to assemble the memory is definitely on the cards for future use!