The airport is about an hour from the center...if that helps
There are several ways to reach the airport, tthe best can depend on the location of your hotel.
Not sure what kind of transportation is available early, but the hotel can arrange for a water taxi -
It is expensive, but staying in the city is worth it.

You have to stay in Venice itself!

The Alilaguna airport boat doesn't start early enough for you, but there is a less frequent night vaporetto service within the city, to Piazzale Roma whence you can get a land bus. I'd stay in a hotel near one of the stops for the night vaporetto and do that. There is a map somewhere on the actv.it website but I can't find it just now - sorry, I need to go to bed! Others may suggest you stay near Piazzale Roma which I admit is simpler but I wouldn't - it's one of the few parts of Venice which is not beautiful and is IMO a bit depressing.

Alternatively, with 4 of you you may think it's worth booking a watertaxi (which only takes c.25-30 mins) and if you pre-book online it's cheaper - current rate is E95 at http://www.venicelink.com/index.php?page=shop.product_details&flypage=000flypage_escursioni.tpl&product_id=86&category_id=12&option=com_virtuemart&Itemid=1&lang=english

Prebook the water taxi...speeding out of Venice early in the morning will feel like being in a James Bond movie. It's hard to leave a place so lovely...that will be a true memory!

Thanks for all of your advice everyone - I really appreciate it. I had thought about staying in Mestre as an alternative, but it sounds like nothing compares to staying in Venice. Getting the water taxi is a great idea for the airport departure. I will check out the website. So, does the water taxi take you right to the airport then? Also, I'm from the US - does anyone know what the standard is for how far in advance one needs to check in? Just trying to map things out in my mind. Our airports where I live generally want you there two hours in advance, but I would imagine that Marco Polo airport may a little smaller than ours.

Water taxis are great unless it is too foggy, in which case they will leave you att Piazzale Roma to find and take a taxi in the predawn hours. How do I know this? From experience. How often does it happen? I don't know. How often is it foggy in Venice?

If it were me I would stay near Piazzale Roma. There are some good hotels near there, and you can start your days with long, enchanting walks toward the center from there. Then, on day of departure, you walk to the bus and it is about 20 minutes to the airport.

How many nights are you staying in Venice?

If you are staying for like 4 nights I would find accomodation just for the last night at a hotel close to the aiport, or at least near Piazzale Rome.

Since your flight leaves at 6.30am, then you have to be at the airport at around 4.45am, add time allowance for water taxis transfer, arrival to airport etc. That would not leave much of the night. By staying at an airport hotel, or at least near Piazzale Roma and pre-booking or arranging transfer to airport would give you time to rest and less night-time hassle of travelling to airport.

In all my years of travelling all over the world, I have never seen an airport check-in counter open before 6 AM.

Never.

Ever.

Keith and I are leaving for Venice on Sunday. We are staying two weeks in a hotel in San Polo, returning to New York on June 11.

I will let you know of our experience getting in and out of Marco Polo.

Thingorjus

I pretty much agree with the Pep. I think the desks don't open until 0545 or 0600, and the OP's flight is likely to be an intra-Europe flight like our domestic ones, so you don't have to be there 2 hours before. This isn't a big airport. It will be busy and a complete madhouse, but everyone will get on the plane.

The water taxi (like the Alilaguna public boats) takes you to a dock about 10 minutes' walk (easy, along a flat covered pavement) from the airport. There are trolleys by the docks, you need a 1 euro coin for each.

How far ahead you normally need to be there depends on your airline & destination. Normally for domestic flights I reckon on an hour, flights within Europe 1.5 hours except budget airlines 2 hrs, and I gather US flights normally ask for 3, but the others are right - check-in won't open that early. Doesn't it say on your flight info when check-in opens?

Although Marco Polo airport isn't that big it isn't that small either, and can be madness sometimes especially in the mornings - probably the fault of the cruise ships, like so much else.

I would find the airport web site and see when it opens. We got to FCO at 4 am and it did not open for half an hour. Then the check in desk did not open until 5. At least we were first in line! But we also could not find any coffee or food at the airport, and our plane did not leave until 6:20 and it took another hour to get breakfast. We were starving! This was an intra-Europe flight, by the way. I don't know what time the transatlantic terminal opened.

Why not check with your airline as to when the check-in desk opens? I have read on other sites that the checkin desk opens at 5a.m. You will have to allow time to get there, whether you take the water taxi (expensive) or the airport bus(pretty cheap). If you are staying a few days you may want to book an airport hotel for the last night.. you wont be getting much sleep but at least you wont have to travel far. You know your family.. are you likely to stay up late, or will getting up and out of a hotel in the wee hours of the morning be a challenge. think about what works best for all of you and enjoy your trip

We are staying 3 nights in Venice, so that might be a good idea staying at a hotel near the airport on the third night. Also, thanks for the suggestions on checking with the airline to see what time check in is. Our first flight will leave Marco Polo on Lufthansa Airlines and stop in Frankfurt (so intra-Europe). Then we switch planes and airlines to Condor and travel the rest of the way back home to Las Vegas. I have never flown either airline before (not having been to Europe and both seem to be European based from what I saw on the internet). Thanks for the offer on letting me know how it goes on your return from Marco Polo to NY Pepper.

I totally agree with Maxima's suggestions. Even if you decided to be at airport at 5.30am, you are absolutely right caroline, they do advise in Europe that we check-in 1 1/2 hrs before and 2 hrs low-cost - I wouldn't know about Lufthansa as I never used them yet)
In my opinion it might be a bit inconvenient to ferry and travel at night-time, and yes as another Fodorite said, it is an airport where many low-cost Europeon airlines land and where you find chaos in the high Summer season, but much quieter in Wintertime, like the Treviso Airport.

On your last day, you can still stay in central Venice till evening, find an inexpensive B&B not too far from airport, or at least close to Piazzale Roma. Some B&B might even offer transfer to airport. But then again, if you do not mind the night-time travel, it should still be ok, but always allow some extra time for your arrival to airport.

I cannot imagine spending a night at the airport....
Piazzale Roma is on dry land...taxis and busses ( don't know how early they start) only 20-25
minutes from the airport.

I would not spend any of my precious time (3 nights) in Venice moving closer to the airport. I would arrange for the water taxi and glide to the airport via canal. Early morning flights, with European connections, are the norm at Marco Polo, requesting an early water taxi is not a special request. And I say this as someone who usually shleps bags on the vaporetto, but with the circumstances you have, plus the number in your party, I would splurge on the water taxi.