Provence Highlights in a Day from Avignon

I would skip Saint Rémy, it is a great base town but not a top destination, in my opinion, unless you are a Van Gogh diehard.
As for Les Baux, it can be overrun / over touristy, and it does not add that much vs Luberon villages. I have never been to Carrières de Lumières though.

I would focus your tour on the Luberon, there is plenty to fill a lovely day full of lavender and cute hilltop villages, and come back to Avignon in time to enjoy the festival vibe. Note that there is usually very little in terms of shows suitable for non-French speakers.

Pont du Gard could be seen the following morning, 2 hours on-site can be enough if you do not linger in the museum.

I took a tour last year with Time 4 Provence — the Best of Provence in one day. It went to all the places in your list plus Pont du Gard. It was a long day, but I loved it, and we had an excellent guide. I thought it was a great way to see the highlights of Provence. We had only three full days in Provence, and we didn’t want to rent a car, so it fit the bill for us. If you are interested, google Time 4 Provence.

Way back in 2014, we spent 2 days in Avignon, and used Provence Panorama for 2 excellent tours that took us to all of the places on your list.

I think 4 hours is a lot for Pont du Gard.

I have done all on your list. With your daughters I would focus on the hill towns for the day. That would be a nice contrast to Avignon. But if you or they are into Roman you could do Glanum near St Remy. A good combo it you don’t do the hill towns could be St Remy with Glanum and les Baux and the Van Gogh asylum just next to Glanum. For les Baux if you have time do walk around the town. There is lovely church with interesting stained glass. And there is a little museum Yves Brayer art. The castle may be crowded but those other sites not.

Thank you for all the comments and suggestions!

There do seem to be a ton of tour options available. I'm leaning towards Imagine Tours because the guide (a local who volunteers his time) would just take the 3 of us, so we could spend as much or as little time as we want in each place.

I did consider the Time 4 Provence tour, but our available day is a Sunday and I don't know that we need to go to the market in Isle sur la sorgue (we are going to Nice after Avignon, so we will see the market there - unless we should see both?) or the Fountain (I understand this is lovely in the Spring when surging but perhaps not in July?). The cost would be similar to having Imagine Tours as our guide, so we could consider this still.

It would be ideal to incorporate Pont du Gard into the day, especially if we can see it in 2 hours (or less - we don't need to see the museum). I'm not sure how much interest my daughters will have in seeing it, but it sounds like a "must see" sight if we are nearby in Avignon.

We are hoping to perhaps see some dance performance at the Festivals (both of my daughters dance) and just take in the vibe. We will be coming from Paris and heading to Nice, so the Luberon (and possibly Pont du Gard) sound lovely. Perhaps Les Baux and St. Remy can be seen on another visit if it would make the day too hectic and require too much driving.

The days are long in July so it is definitely possible to have your private tour take you to Pont du Gard after the Luberon. Or vice versa if it's a hot day.

Isle sur la Sorgue on a Sunday has a big antiques market and it would take the whole morning, the town gets swamped. Fun if you like antiques, though.
As for Fontaine de Vaucluse : a bit of a tourist trap, and increasingly frequent drought conditions means that it is rarely gushing. For me it's a pass, and for what it's worth, Michelin Green Guides progressively downgraded it from a *** to a * sight over the years.

Four hours for Pont du Gard is not necessary.

I agree that Fontaine-de-Vaucluse is totally skippable.

L'Isle-sur-la-Sorgue is a pretty town, but it's hard to appreciate that on market days with the booths everywhere. The markets are fun, but I ended up making a second trip to the town on a non-market day so I could really see it.

When limited time is available, I wouldn't feel the need to see a whole bunch of markets to the exclusion of other things, though I do enjoy casually browsing in them. (I'd say I'm closer to the non-shopper end of the spectrum than the shop-till-I-drop end.)

Thank you for the feedback. It sounds feasible to see Pont du Gard in the morning (or at the end of the day) then spend the balance of the day in the Luberon. We will skip Fontaine-de-Vaucluse and L'Isle-sur-la-Sorgue, given it is a Sunday market day. It doesn't sound like there will be enough time to see Les Baux or Saint Remy as well and it sounds like we should see Pont du Gard instead.

Are there other places to see lavendar in the Luberon besides the Senaque Abbey? I understand it can be swamped with tourists, but we can always just do a quick photo stop. It would also be lovely to see the sunflowers, so any suggestions on where to see those are also welcome.

Besides Roussillon and Gordes are there other hill towns in the Luberon we should try to see? Menerbes?

Agree about Sénanque crowds. The main lavender patches in the Luberon are between Saignon and Buoux. It's not that far from Roussillon, but there should be some closer ones - I vaguely remember some between Joucas and Lioux. A knowledgeable guide should be able to find them - and others I do not know about!

As for other hill towns: your driver could stop in Joucas between Gordes and Roussillon. It is tiny, pretty, empty: an enjoyable 20-minute stop!
The Pont Julien Roman bridge, back on the main road down from Roussillon, is also worth a stop.

As for sunflowers, they are all over France and they can look a bit burnt in July. You are bound to see some fields as you travel around the country, but I would not make specific plans to see them.