It would help to know how many there are in your group and when you will be needing this transportation.
Personally, I can't imagine being stuck in a van or 2 cars full of people on the highway for so many hours. Trip time will expand depending on the need for gas stops, rest stops and potty breaks for everyone, especially the driver(s). And you will all travel at the speed of the slowest one(s) in your group.
Keeping all that in mind, I think taking the train would end up being much more comfortable and more fun. Everyone can move around and not be trapped in seats with seat belts. They can eat at will, play cards, chat, you get the idea. Plus, depending on the size of the group and their ages, it could be a lot cheaper.
Out of curiosity I checked Trenitalia.com
(https://www.trenitalia.com/en.html) for Thursday, 5 May 2022 as an example of the possibilities. Frecciargento 9724 departs Venezia S. Lucia at 10:48 and arrives at Milano Centrale at 13:15, a 2 hour, 27 minute trip. Frecciargento trains operate at speeds of up to 250 kilometres per hour (155 mph).
Taking this route, there's only one train change with a generous 50 minutes to make the change. InterCity 669 departs Milano Centrale at 14:05 and arrives at Monterosso at 17:05, a trip of 3 hours.
Both trains go through many towns as well as countryside, so you can see a lot along the way. They will make quick stops, but you will not have to move except when you change trains in Milan. Your seats will be reserved on each train, so if you plan ahead, you are more likely to be able to sit close to each other, if that's what you want to do.
I must admit that except for an occasional taxi, I've never hired a driver to take me anywhere that I could get to by metro, train, plane, ferry or bus. And I love going by train.
Here's a link to Trenitalia's info on their Fecciargento trains: https://www.trenitalia.com/en/frecce/frecciargento.html
In the link below, see what the Man in Seat 61 has to show and say about train travel in Italy, including interior pictures of the kinds of trains, how to handle luggage, info on train stations and much more: https://www.seat61.com/train-travel-in-italy.htm