Oh awesome! I’m really excited

That’s definitely a good point about the sheet instead of a blanket.
I hadn’t even considered leaving them alone the first few days but that totally makes sense. The ducks are really sweet and have been handled a lot since they were a day old. The kids are outside with them playing every day! So they are used to being around people, but the few times I have gone over there one of the ducks will run in the coop and hide. So they definitely know who their people are and will have to get used to me. I would love to hear as much as you’re willing to share about socialization!

thanks so much for your response!! Much appreciated.
I think having them in a crate, even if it is in the back of a truck, is better than having them wander around the inside of an SUV. First of all, you likely underestimate the projectile poop - which becomes more frequent and watery when stressed. Second the speed at which you will travel and any passing vehicles is very scary to my ducks and that is where covering the crate comes in.
I have used the following method with great success to tame terrified ducks into friendly pets that follow me around, and even hop into my lap. Since your new ducks are already friendly with their current family I'm sure they will just need some time and gentle understanding from you. You could start by giving them space to adjust to their new surroundings, then follow my method for as long as it takes for them to get used to you. I suspect it won't take long.
I avoid anything scary. I pay attention to what scares them and I don't do it. I don't make direct eye contact - that's what a predator does before attacking. Instead I look near them. If they are afraid of me being tall I crawl anytime I'm near them and stand up further away. If they don't like being startled I talk as I approach. My ducks didn't like me walking directly at them so I walked in big semi circles around them. (These things are mostly temporary.)
I make every experience positive. I give them their favorite treat everytime they see me. For my ducks that meant I threw them mealworms when I passed their aviary. This also meant I didn't force them to cuddle/accept physical affection. I still don't. If they sit next to me or hop into my lap, cool. But I don't hold them there.
I spent lots of time hanging out being still. I sat near them, being not scary or noisy, doing calm things. I knitted, read books, took naps, ate dinner, ect.
My ducks used to run in the other direction when they saw me. After a few months they ran to me. I became the bringer of good things. When they see a scary hawk they run to me and lay on my feet. We have a great relationship, but I do respect that they are ducks. My ducks are frightened of strangers, but less than they used to be of me.
Keep us updated on how things go, please!