What can be used to ensure that the pallets stay intact during transit?

if they are standard wooden pallets going inside a van, then shrink wrap should hold the contents of the pallet together fairly well. If this has to go on an open deck truck like a flatbed or step-deck, then you can use cardboard siding with metal banding and shrink wrap, and request a drop tarp to cover the pallet(s) to help preserve the shrink wrapping.