What is the timeline and how big are the trees? If you've got a few weeks before they have to go, I would recommend digging around the largest possible
root ball that you will be able to lift, then boxing or bagging them with a good
compost mixture. Use a sharp spade to cut the
roots as cleanly as you can in the shape of an inverted cone. Prune back the branches to reduce the transpiration demands and
water well. Shade cloth will also help.
If you don't have the lead time and they need to go now, the same process applies without the time spent in the boxes or bags awaiting travel. Speaking of travel, covering with tarps is important if they're going in the back of a pickup or on a trailer at highway speed, as the wind will really suck moisture from them. Having planting holes ready at the other end is ideal, but if you can't manage that then keeping them in a nursery at the new location and planting them in the autumn or winter
should be ok.