Road trip vs Train: Disneyland Paris to Loire Valley to Toulouse and Avignon

Whether or not this is too much driving depends a lot on you and your family, and how well your children tolerate spending hours every day in a car. Given the driving time from the Loire, what is the purpose of a single night in Toulouse, other than to break up the long drive to Avignon? Have you looked at a car rental broker like AutoEurope for price comparisons? Autoroutes (the equivalent to US Interstates) are as good or better than what you might have at home. Be aware that tolls will likely be involved, and the cost of gas is not an inconsiderable cost factor. Look at ViaMichelin for distance, time, and costs of each leg of your proposed trip.
And have you considered taking the train from St Pierre des Corps (in the Loire? ) directly to Avignon? SNCF is the French rail company.

The kids wanted to see Toulouse machine museum but it's also to break up the drive. I've looked at Loire to Avignon but it's going back to Paris and then to Avignon making it a 5hr journey.

Since you're only planning to stay one night in Toulouse, I'd be curious to know how you intend to drive from the Loire Valley to Toulouse (6 to 7 hours), visit the Halle de la Machine in Toulouse, and be in Avignon the next day (4 to 5 hours by road from Toulouse), while looking for the most cost-effective options.

Also note that road traffic is particularly congested on French highways on summer weekends, especially heading south and along the entire Toulouse-Avignon route.

neshakum,
You would need two nights in Toulouse to fit in the museum visit. Viamichelin.com is good for getting routes and drive times, but they do not factor in time for getting gas, meals, bathroom stops, etc. For your drive TO Toulouse, I would add 1 1/2-2 hours to what they say, as you will also have to find your way within the city to your lodging, find parking, etc....basically a whole day on the road, after checking out of your Loire lodgings or Disneyland. Likewise, going on to Avignon will pretty much take up another full day on the road. Toulouse machine museum or not, this is a lot of time spent in a car.

Perhaps you might forgo the Avignon part of the trip and move from Toulouse to the Dordogne area (2 1/2-3 hours). It is a great location for lots of variety that will satisfy a family. We spent 10 days there with our kids and grandkids (We were seven people, 9 to 80 years of age.) Have you determined what your priorities are for the Avignon region? The "south of France" is huge. Do you have specific things to do and see or do you have a picture in your mind of what you hope it to be? The Dordogne is in the south. So is Provence, the Riviera, Bordeaux, the Basque region, Marseille, the bas Alpes, the Rhone valley.....if you give us an idea of your hopes or expectations for this part of the trip we might be able to give more helpful advice.
Also, how much time do you have? How many days will you spend at Disneyland? What are the children's ages? Are you counting arrival and departure days in your total time?

We traveled with our two kids at 8 and 10, 18 and 20, 43 and 45, plus grandkids at 9 and 12. Some of our experiences may help you in your planning, but some more info would be useful.

Thanks for all the tips! We're there for 3 weeks. So I've reconsidered the time it's taking to drive and instead booked Loire valley in after Paris and before Disneyland. I'll now take the train from Disneyland to Lyon and either spend a day or two there and continue to Avignon via rental car and use the rental car till we leave via Nice airport. I do save a significant amount renting from Lyon instead of Avignon for some reason. Also, I think we'll hit Grignon on our way to Avignon. I'm seeing that there's caves and lavender there. After Avignon, thinking of going to verdon gorge for a night or just spend the day there and then go to Antibes. Hoping to base ourselves in Antibes for the rest of the almost 7-9 days for beach time. Please let me know if this sounds more reasonable. Is there a better spot to base ourselves in instead of Avignon for two days?

neshakum,
Your new plan sounds much more practical and enjoyable. Well-thought out. You might want to get a Michelin map for the area you will drive in. A paper map will let you see the overall picture and provide more than directions (ala Google maps, etc.), plus maybe point out some stops.

Regarding car rental rates, they're often high when you look months ahead of high season, then come down closer to the date. Book a refundable car now, and check again in May or even June.
Last summer, I saved about 25% rebooking my car just 2 weeks before an August trip to Toulon - a similar car rental market to Avignon, in a super peak period.

Have you got the right information about Antibes? The city itself, between Cannes and Nice on the French Riviera, is one of the most expensive in France (and even more expensive in the summer).

I'm just saying this because you seem to want to save money on car rental, and those savings will vanish in a single day in Antibes.

Do you mean Grignan? Grignon is near Albertville where the winter Olympics were held in 1992. Grignan is where you would find lavender and is in the Drome region, closer to where you will be. Be careful with your French spelling, especially when inputting in gps, etc. There are many similarly-spelled names of places in France. Just like Aix...there is Aix-en-Provence and Aix-les-Bains, two different towns, with suffixes to differentiate, and then places with just one letter difference, like Grignan and Grignon. Auto spell and autocorrect can give you problems. (You see it in the forum questions, like TVG instead of the correct TGV, or CGD instead of the correct CDG.
Il faut faire attention, s'il vous plait.

Thanks for the tips! Is there a spot that might be better than antibes with nice beaches and restaurants?

Yes, I meant Grignan. Thanks for the correction.

Also, thanks for the mention about the car rental being cheaper. I thought it might be cheaper if I book earlier, I guess not. Good thing is I did get one with cancellation.

Nothing to do with driving, but I recommend using one of the several Disney hotels for your stay. All have easy access to the parks and if you book a package with tickets, you get in an hour before general admission. They do use dynamic pricing so check your dates to see if it makes sense. Regardless, be sure you download the app as it has very accurate wait times for rides.