I'd just scoop out a wide hole with the front loader about half the depth of the pot [should be really easy in sandy soil], pull it out of the pot, rough up the root ball a bit, set it in the middle, then fill in the hole with some fertilizer and compost, mixed with the removed soil in your front loader, then dumped back in the hole. Don't over supplement your native soil, otherwise the roots won't want to leave the cozy new pot you made them and venture into the regular soil where they really need to live. Tree roots don't like clean augered holes, which can just end up being a pot drilled into the ground for them to rot in, although not so much with sandy soil. Trees appreciate a mounded planting anyhow, rather than sinking into the ground for the crown to rot... and they will always sink after planting. Not so much a worry with good draining sandy soil, but with our clay on top of hardpan, they need all they help they can get during planting. For watering, I use 1/4" dripline on a hose that I move from tree to tree, looped around the tree. Just keep the water from puddling on the crown by not planting too deep, and force the roots outward by watering away from and around the new tree... make them look for the water and they will find it. Just enough water on the existing root ball to keep it healthy, but still wanting more. Also, if they are grafted trees, ensure that the graft is never buried.