looking for tour from Rome to Pompeii/Amalfi coast what uses Vans, not buses

What month will you be there? Whether the vehicle is small or large, I would not want to be in one pretty much from spring to fall--the traffic is really that significant.
Can you spare a night away from Rome? This is really a snap to do by yourself, but I think it is too much for one day no mater how you do it. One night does make it so much better!
If you have only one night, this is how I would do it: Fast train to Naples, train to Pompeii, train to Salerno, stay a night, visit Amalfi Coast by Travelmar ferry in the morning, ferry back to Salerno, fast train to Rome.
If you are trying to do it in one day, forget Vesuvius--I just don't see how it could be possible to do all of that.

Many years ago we were on a cruise with a stop in Naples and we did a tour that included Pompeii and the Amalfi Coast. I don't recall the tour company but I wouldn't recommend that all in one day, it's too much of a whirlwind. Even from Naples we spent more than half our day in a vehicle.

In April 2023 we based ourselves in Sorrento for 2 weeks and did a day trip from there of the AC with Mondo Tours, and even then, of a 9 hour tour, 4.5 were in a vehicle. Mondo Tours also does tours of Pompeii, but you'll meet your guide on site. A 2 hour tour is a good start but it just hits the main highlights. We spent about 10 hours over 2 days at Pompeii.

Month and year?

https://community.ricksteves.com/travel-forum/italy/pompeii-day-trip-from-rome-2c38f926-9036-480d-95fd-403dd7694e4a

https://community.ricksteves.com/travel-forum/italy/pompeii-and-vesuvius-69e8366c-1e75-4a14-a0bc-0677269492d1

8 hours and more in a van just to get there and back, no thanks. You may want to search (top left, blue menu) for more discussion of possible motion sickness from Sorrento to Amalfi. We didn't feel sick, but that was in a car-and-driver sedan, starting in Sorrento.

I should add this would be at the end of April this year, around the 24th - 26th or so. We are even considering a night's stay over somewhere, so it doesn't become one long slog of a day. We are both older adults, late 60's and are fine with walking for a long time. and if we were to stay over, it would need to be the 26th or 27th, because from there we are heading to Florence, via train.

Thank you.

That's great because you don't have to worry about getting to Pompeii at opening time to avoid afternoon heat. I am all for splurging when it makes sense, but you can really do this yourself and have a great two days -- and put the savings toward the hotel and meal.
You can even stay ON the Amalfi coast if you wish, though I favor the villages that are closer to Salerno.

Walks of Italy has one. I have no experience with it yet. I’ll be doing it after your time there

I recommend Askos Tours, whether you decide to do a day tour from Rome, or spend a night in Pompei.

https://askostours.com/

If you decide to spend a night in Pompei, I highly recommend this hotel:

https://www.hotelforumpompeii.com/en/

It is very realistic and sensible for you to consider spending one night. The distance from Rome is just soooo far.

There are 3 hour and 1:10 trains to Naples. But that still leaves you an hour from Sorrento, which isn't even "On" the Amalfi Coast. That's another 45 minutes (by car, usually, but a bus could possibly work in April) to Positano. I was underwhelmed by Positano, but it certainly was (like for you) a "must see" on our first trip to this area. BTW, that was our fifth or later trip to Italy. I don't consider it part of an initial visit to Italy, which is classically Rome-Florence-Venice.

I do not recommend staying in Pompeii. No one will ask you if you enjoyed your visit to Anaheim when you go to visit .... .... you know. Most people might stay in gritty, disorderly, historic, food-rich Naples, or Sorrento, where English tourists ask on Trip Advisor, "ow much is a Pint????" We spent 5 nights in Sorrento, because its so well located for daytrips. (It is NOT a serious "beach resort". And it's not very historic.) We did well, at a luxury cliff-front hotel, where we paid extra for a view of Vesuvius from our bed, and a balcony. (Ambasciatori Grande.) Either Naples or Sorrento provides a gritty, crowded, hot commuter rail line to all five of the most popular ancient "Scavi", including Pompeii and Herculaneum.

This is relatively expensive area. If you stay overnight, you may want to do all your visits on your own, to save money. Two tours, or even two 8-hour car-and-driver (the driver is not a certified guide) could easily be 400 Euros a day. A group tour would be less, of course. (We are independent travelers.)

Would you consider leaving Pompeii for another trip?
What about visiting Ostia Antica, MUCH more convenient than Pompeii, from Rome?
The only way I would ever think for a second about doing a trip from Rome is if I wanted ONLY to visit Pompeii with maybe a stop in Naples.

Have a look at Context Travel...very highly rated small group operator. They use a combo of train and private car to visit Pompeii and the Naples Arch Museum, from Rome; their guides are highly educated:

https://www.contexttravel.com/cities/rome/tours/pompeii-full-day-excursion-from-rome

There are nice hotels in Pompeii if you wanted to spend the night. As well as some excellent restaurants that people travel to even when they are not visiting the site. (Il Principe is one)