Cotswolds Options

Offering an alt idea - there is a Mad Max Cotswolds tour that runs out of Bath on Mon and Wed that takes you to most of those places on a small group mini van style one day tour. That would allow both in the party the chance to enjoy the scenery and commentary and then still pick up your vehicle to continue on to your Salisbury leg. As an aside - I’ve booked a similar situation based on the positive reviews of Mad Max here on the RS forum but don’t have that direct experience yet.

I've been on the Mad Max tour from Bath and can absolutely recommend it. I had such a wonderful day. I think Castle Combe was my favorite. Take a look on their website. It was a great day.

Thanks for the suggestions. The van tours sound nice but I forgot to mention that my wife is prone to motion sickness and doesn’t do well on van tours. I might use the tour websites for itinerary ideas.

I forgot to mention that my wife is prone to motion sickness and doesn’t do well on van tours.

I too am prone to motion sickness and my doctor had suggested I take non-drowsy Dramamine before trips. Ask your doctor if something like this might be a solution for your wife. Notice I say to ask your doctor.

If you can solve that problem, you can take a van tour, which is the easy way to see the Cotswolds, IMHO.

You have a trip to Moreton-in-Marsh in your schedule, according to your post. It's one of the pick-up points for this tour, which I highly recommend: Go Cotswolds, owned and run by a family who live in Stratford-Upon-Avon.
My husband and I have been on several of their tours. Excellent! The tour makes several stops with time for you to explore each village on foot. There are 2 different tour routes. I've been on both and prefer the first one listed here. I can make recommendations in each village for lunch or coffee or tea plus cake break mid-afternoon, if you wish.

https://www.gocotswolds.co.uk/product/cotswolds-in-a-day/

https://www.gocotswolds.co.uk/product/secret-cotswolds/

From Oxford, we’ll take a train to Bristol for a three-night stay. During our time there, we plan to take a day trip to Bath by train.

I don't know what you'll be doing in Bristol that warrants a 3-night stay, but my opinion (which...you asked us for) is perhaps one night Bristol, then train to Bath to spend 2 nights would be better. There's a lot to see in Bath and it is lovely. Excellent restaurants all over the place. Gorgeous places to do walks around town or in its parks. Walk down the canal/waterway path to Bathampton, have lunch at a pub, walk or train back to Bath. Several great museums; the Holburne Museum of Art is excellent.
You'll want to see the abbey and the Roman Baths for sure.

When leaving Bristol, we'll rent a car and drive to Salisbury for a few nights.

One of the easiest train trips in all of England (IMHO) is the short ride from Bath to Salisbury. Car is not needed here.
However, if car is the way you choose to do your trip, it's your trip.
Many forum members here enjoy driving in England, and I am sure they'll be along shortly to tell you so and to encourage you to get a car. Just as some people like vanilla ice cream and some prefer chocolate; everyone has a preference. There's no right and wrong here.
I was merely trying to give you some options.

By the way, good call on spending several nights in Salisbury. Lovely place.

We have rented cars in the UK a couple of times and did just fine.
My advice is the not speed (many towns have speed cameras). Also, most Brits are very polite drivers.
It takes a day to get used to driving on the left, so just take it easy and in particular focus on where you are going during turns at intersections.

Further, roundabouts are common in Britain, just take it easy and you will get through them just fine.