Gel coat on the keel can be fixed easily for not a lot of money. The fun I've had on sandbars with friends is well worth the cost.
Actually though, if you do it carefully and there are no rocks, then it causes very little damage. We have a 3-6mph current, so there can be no anchoring a few feet off the sandbar.
I had my 28 Pantera for 5 full seasons and it was probably beached 8-10 times a summer. The gel was starting to get a little thin on the keel, but there was no real damage.
Here is a pic.