I LOVE mountain laurel and I have several I have planted, different colors and flower shapes, on my small, NJ property. They just finisheed blooming and they were AWESOME. They can, however, be tricky, especially when first transplanting from pots to the ground. For larger plants, they seem to take a couple of YEARS to adjust. I have actually had better luck planting small, liner size plants or transplanting from one location to another. They have shallow, fibrous roots. I think the shape of the roots is all wrong in a pot, and it takes them some time to spread out surface roots.
Make sure they are not planted deep, they should be planted shallow, on small raised areas amended with fine pine mulch, peat etc. They want that combination of acid soil and "moist but well drained". They will need to be watered often, but should be planted in a location where excess water will drain off reasonably quickly. Good luck with them!

They are planted relatively high on a slope in an area with a lot of natural mountain laurel, so I know they will adapt to this location. My concern is more immediate, though, in that I am afraid they won't live long enough to establish themselves. I'm wondering if I should dig them out and replant with more material that will enhance drainage or if I should let them be and see what happens.

Have you called Rare Find to see if they have any recommendations? In past dealings with this nursery I've found them to be very helpful.

I have some "wild" mountain laurels here that have survived all kinds of abuse, including coming back lush and full after having been cut almost to the ground, but they're species and well-established and that could make a big difference.