Late arrival in Venice

Here's the timetable for ACTV bus #5 from VCE to Piazzale Roma. The last bus leaves at 1:10 AM, which might be a problem if the flight is late, and/or you have to clear immigration and/or wait for checked baggage. Unless your hotel is close to Piazzale Roma, you'll need the vaporetto which doesn't run after 11:41 (see timetable). Likewise, the Alilaguna Orange Line service from VCE to Rialto ends at 11:45.

Maybe you could spend a whole lot on a water taxi, I don't know when they stop running. Or, as I did last month after a midnight arrival, spend the night at a hotel near the airport. I stayed at the Parkhotel Annia but its shuttle had stopped running and I overpaid for a "private taxi" to take me the two kilometers or so. An alternative might be the nearby Marriott, which I believe has a paid shuttle. You could check their website or contact them to see about its hours. Then, next morning, you can shuttle back to the airport and take either the bus + vaporetto or the Alilaguna into the city. That worked well for me.

Rather than choose a hotel for a multi-night stay based on whether you can get there from the airport after midnight, I'd suggest choosing it for whatever other reasons matter to you -- location, cost, amenities, atmosphere, etc. Then crash at an airport hotel the night you fly in. Hope this is helpful.

It might be easier to find a lodging that has a late night/early morning ( 24hr) front desk so you can check in, and ask them how to get there from the airport at the time you will be arriving.

Staying in the area of Piazzale Roma or the train station will be convenient for your arrival and departure to Padua. Make sure the hotel you plan on staying has the ability to check you in at that late hour. The smaller, less expensive places will be shut down for the night.

There are a lot of hotels just a short walk from Piazzale Roma that will be "Venice". Staying right on the piazza will involve auto traffic, buses, tons of pedestrian traffic. But just a few steps away it will be quiet canals.

I suggest staying out at the airport and coming into Venice in the morning.
The place is tough finding addresses, etc. in the dark, especially if you've never been there.

I too would recommend staying by the airport the first night. Also when you get to Venice there may be visitor only routes which could increase your travel time within Venice.

you'll need the vaporetto which doesn't run after 11:41

Sorry, but you are wrong. After the last run of the day the vaporettos night service kicks in.

There are always (wheeled) cabs waiting in front of airports when there are flights arriving. Just like there are people to ask for help if you get lost. It's Venice, not the Sahara.

If you can avoid it, do not waste the first night staying close to the airport: Take a land taxi to Piazzale Roma and a night vaporetto to your hotel/b&b. You can Walk around Venice on google maps before actually being there.

Yes, the "N" boat schedule.
http://actv.avmspa.it/sites/default/files/Orario%20linea%20N%20dal%205%20nov%202018.pdf

The No 5 bus schedule from the airport. Venezia Corsia A1 is the bus stop in Piazzale Roma.
http://actv.avmspa.it/sites/default/files/attachments/pdf/UM/U-5.pdf
Last bus is at 1:10 am. Combined bus and boat ticket is 14 EUR. If you decide on a multi-day vaporetto pass, you can include the No 5 bus from the Airport for 6 EUR at the time of purchase. Otherwise, it is an 8 EUR ticket.

There is a Courtyard by Marriott right next door to the airport...far enough away that you need a taxi but just about a 3 minute ride. Very easy. Clean, modern hotel with an exceptionally good breakfast buffet.
The next morning you can catch the bus to the main bus terminal in Venice or taxi back to the airport and take the Alilaguna boat.
If you want to take the bus it's cheap and you can buy a ticket from the front desk of the hotel. The stop is directly across the street from the hotel and there is room for luggage. About a 15-20 minute ride into Venice.
Trying to navigate into Venice to find your hotel after midnight will not be fun, especially if you have to drag your luggage through the narrow streets and over the bridges trying to find it. If your hotel has a water entrance, which some do, you can take a private water taxi but it will cost you. If you choose this route make sure that the hotel has a 24 hour desk.