We will be flying out of Venice to Frankfurt at 7AM. Should we stay at a hotel near the airport the night before leaving, given that we will have to be there at 4:30AM? Is it hard to get from the heart of Venice to the airport at that hour? Can someone recommend a reasonable hotel near the airport for the one night?
We've stayed at the Titian before and found it nice. There was even breakfast very early.
One of the worst oversights in booking Venice is an early morning trip to the airport from the main part of the city. This site has numerous posts of early morning flight problems to Venice-Marco Polo. To use reasonable transportation (buses, Alilaguna, etc.) you just can't have a flight depart earlier than 8:00am. Even though transportation services start as early as 4:00am, it's a struggle to get there in time for the proper check-in.
What traveler's are forced to do is hire a water taxi for high-speed water transport to the airport. It's currently running 100E-115E ($155-$170) to hire a water taxi.
Yes you can have a water taxi standing by at your hotel at 3:30am or so but look at the expense. However, I would strongly suggest staying near the airport. There are a few hotels there. I would suggest the Marriott Courtyard which is .8km from the airport. 132E/night. Not sure about shuttle.
You might also look into the Titian Inn Hotel and Residence. It's also nearby the airport and, they have a shuttle. http://titianinn.hotelinvenice.com/overview.html?source=-titian+inn+hotel+venice
I think that you can get good rates on this hotel on www.hotels.com or www.venere.com.