You can stay close to Venice and go in Verona (or "fair Verona" if you have a Shakespearean taste ;) ), and maybe pass by Padua or Vicenza.
Alternatively, Bologna is close enough to Florence to need only one hour by train to get there.
> We're also going to Florence and Rome (Venice was in between those two)
Considering that going from north to south, you have Venice, Florence and then Rome, why was that in the middle of the trip and neither at the beginning or end of it?

I'd avoid Venice only because it's a bit out of the way from Rome/Florence. Honestly I'd visit Naples if I were you. Christmas is coming so it's also a great time to visit (Naples is famous for its presepi, i.e. nativity recreations).

Venice and its population deal with floodings on a regular basis. It's really a high tide, increased in magnitude by winds and bad weather. As such, "acqua alta" is an event that typically recedes in a matter of hours. This one has made the headlines, but most shops, restaurant and services will be restored straight away. Some tourist attractions might be affected for a while, mainly historical buildings that are not usually hit by the high tide and end up needing restoration, but you should really check on a case-by-case basis depending on what you were planning to visit.

I just checked the forecast for acqua alta for that day and it is forecasted normal tides that day. There may be some areas that see some water come up but less than 10% of the city will be affected. That's worst-case scenario.
Many times these extreme high tides can be predicted. What can happen, like in yesterday's case, is that high winds, tons of rain and an already high tide all come together to make it a disaster. We have had weeks of almost non stop rain so all the rivers are dumping tons of water into the lagoon. Then the winds kept all that water in the lagoon with high tide getting pushed in higher.
I was there on Monday when the acqua alta started and it was not bad at all. The areas affected were all around St Mark's square as that is the lowest area. While I was there, walkways were needed around that area for about 2 hours until the tide went down. Then everything went back to normal.
On the day you are thinking, there is not likely to be any problem at all. The train from Rome is not ordinarily that bad, but yeah after a long flight it is a bit much. I would go to Venice if you are already planning a trip up to the northern areas. Otherwise I would just stick to Rome and the surrounding area.
If you have a chance to see Venice, I would stay a couple of days instead of trying to just do a hit and run in one day. Definitely don't avoid it because of the possibility of high tides.

Not the best season to visit Venice but extreme tides like the one that happened yesterday are kinda rare. By the 24th almost everything should be back to normal.

Skip it, Venice is a tourist trap.

flooding lasts a few days, and expected again in the coming days.
but in Venice they are used to it , Nov-24 is far away, if there are no others they will be ok.

You are gonna be fine! Venice is wonderful off season with less crowds.

If I were you, I would go... A friend of mine has gone recently and he assisted at a flooding, but a normal one. Consider that almost any of the venetian floods are dangerous, they are just a bit annoying, but for sure they are not dangerous (It didn't happened something like the recent case since 1963 or something like that, I don't remember the exact year). However I don't know where you would want to go, but If you don't want to go to Venice, I think Milan is a pretty good city to visit... You just have to take a train from Venice and you are there in 1h. Hope it did help and have a nice journey :)

We arrive in Venice Saturday morning. Do you think we should keep our trip or detour somewhere else?

I'll be in Venice a couple days after you and I am not going to cancel. Flooding issue should be better by then, I hope.

It's gonna be fine. You might see some damage here and there. The WORST thing that can happen is that water will arrive at your ankle in some parts of Venice. Just get a pair of boots (sold everywhere on Venice) and you are gonna be fine!

Il caso vuole che la nostra scuola sia gestita da un gruppo di incompetenti. In poche parole, solo domani pomeriggio tardi sapremo se effettivamente si andrà a Venezia.
Abitando a 70 metri da scuola per me non è un problema, diventa un problema per tutti i ragazzi che si fanno quotidianamente più di un’ora di autobus, i quali, per evitare di svegliare i genitori alle quattro del mattino, andrebbero a dormire da alcuni compagni che stanno vicino alla scuola portandosi le valigie sin dal mattino.
Un’idea era quella di andare a Padova e/o Verona al posto di Venezia, tuttavia la maggior parte di noi aveva aderito perché interessata alla Biennale, quindi l’idea di un ripiego non è stata presa bene.

Io sinceramente rimanderei, non sono di Venezia e non so se ci siano stati danni in zona Biennale, ma ora come ora credo sia meglio aspettare qualche giorno. Ho visto che la Biennale chiude il 24 novembre, la tua scuola è vicino a Venezia? Lo chiedo perché se non siete distanti potete provare a fare un salto settimana prossima (nella speranza che la situazione sia migliorata).

Siamo ad Urbino, quindi in quattro ore di bus si arriva tranquillante a Venezia, anche io preferirei rimandare e non rinunciare alla Biennale. Ma sono abbastanza sicuro che la scuola non abbia voglia di impelagarsi nelle pratiche di posticipo (o rimborso) con l’agenzia.

Per "vicini a Venezia" intendevo se foste in Veneto o massimo in Friuli-Venezia Giulia, già Urbino-Venezia è un bel viaggetto...e capisco che "buttare" via una gita non faccia piacere, ma del resto abbiamo visto tutti cosa sta passando Venezia, ed è il motivo per cui in ogni caso rinuncerei, non riuscirei nemmeno a godermi il viaggio.

Thanks, are you in venice by chance?