Driver or train from Venice to Ravenna?

I think you would do fine with the trains. The site for the national railway is trenitalia.com. You can set it for English, but you will still need to use Italian names for cities. When looking up schedules, you will need to set an early time (say, 7 a.m.) as well as the date in order to see all the trains; Italy uses a 24-hour clock. When I looked up 'Venezia-Ravenna', I saw that you have to change trains in Bologna, and that the whole trip takes + or - 3 hours one way. Starting at 120 days out, you may be able to save money by reserving an Economy ticket online on the high-speed train between Venice and Bologna, but you are committed to that train, so it's a gamble to do that the day you fly in. You can just buy your ticket when you get there, instead. The Bologna-Ravenna leg is on a Regionale train, which never sells out and you don't reserve.

Venice has frequent connections to Ravenna, involving just one change. The journey takes some 3 hours and can be as cheap as EUR 14,30. (Check for timings and prices at www.trenitalia.com/tcom-en).
But staying in Venice has its obvious advantages, especially after a long flight. If you think three days is too much, you can always have an easy day trip to attractive Padova (Padua) or Vicenza. These cities are served by frequent trains, including the cheap Regionale trains and involve no changes. (Schedules on the same Trenitalia site.)

I'd stay in Venice. Three days there is not too much. Wander the back streets far away from San Marco and Rialto, have some gelato, familiarize yourselves with the vaporetto system before your friends arrive, find a scenic spot for photos at sunset.

Thanks so much for your responses--I will definitely mull them over. Wondering if it's one of those ideas that sounds great now, but in reality I'll be kicking myself that, once again, I bit off too much.😊

Do you have a particular interest in early Christian mosaics? If not, don't try to jam it in to your itinerary. I spent four nights in Ravenna on my fifth trip to Italy and loved it, but you can see some amazing mosaics in Venice without the hassle of going to Ravenna. In particular, the mosaics in Basilica San Marco are amazing. If you're also going to Rome, I can point you to quite a few churches with early mosaics.

There are beautiful mosaics in churches on the island of Torcello.

I would try for an overnight in Ravenna, but adding more travel time to your first day on the ground depends on how you handle that long flight.

The mosaics at San Marco (inside and outside) aren't shabby either.

Much as I love Ravenna, it's too much. From Venice (Mestre), the first train after 8.00 am is at 9.37, arriving in Ravenna (changing in Bologna, a rather large station) at 12.27. Then you have to find your hotel, check in and drop your luggage. By this time, you'll probably want to have lunch. Returning to Venice, you have a 3 hour-plus ride to Venice (Santa Lucia) and then 1/2 hour to an hour to get to your hotel. So you have a short afternoon (when you're zonked) and a morning to see Ravenna, before rushing back to Venice to meet your friends in the evening.

Thanks to all for your very helpful responses. I think I'll scrap Ravenna on this trip and instead enjoy the mosaics in Venice...

For the San Marco mosaics, visit mid-day when they are floodlit and best seen. When I was there several years ago, it was from 11.30-12.30. Also visit their museum, which includes some up-close views of the mosaics and access to the balcony ovrlooking the Piazza.