Hi,
Just as an FYI, this probably should have been asked way prior to you going to you could get adequate supplies for them.

I traveled from Ohio to Texas in 3 days so for the health of the bunnies, you should break it up into 2 or 3 days. They can not be confined for that long. They will need time to stretch their legs for a significant amount of time each day, so ideally have large cages(I had 2 huge ones for each pair 2ftx2ft) so they could hop around in it. When you stop for bathroom breaks with the dog, make sure to get them out, let them run around on the car seats if you can so their gi tract can stay active. Being caged up for so long can lead to stasis as they can’t be active. It’s best to have individual carriers for each bun since you want to drive straight though but honestly, you’re gonna get sick of driving and want to break it up anyways into a couple of days. And with all the potty breaks for the dog it will likely make that happen.

You need to make sure they eat during the trip, ( keep fresh food and water in their carriers at all time,if they don’t you will need to force feed them all critical care and ideally give sub q fluids so they stay hydrated to keep their tract moving but you can force feed them water( depending on their size, 1.5kg around 100ml a day, 2.5kg 150-200ml a day and goes up from there)I didn’t know any of this information but then again we didn’t travel long everyday because of my 4 buns and my moms 2 dogs so they had overnight to eat veggies in hotels. Stress alone of the trip can cause stasis so making sure they eat is the most important thing.

You probably should have gotten anti nausea meds from the vet since buns can get nausea and can’t throw up to relive themselves it may cause them to feel really really sick and not eat and then cause stasis.

I hope the trip goes well and let us know if you have other questions