I was groomsman at a beach wedding way back in the day. I wore my best pair of dress shoes. They weren't ruined by spending 30 min. in the sand. I'd do the same today - just wear the shoes that best suited my outfit. If they need polishing afterwards, so be it. They will need polishing eventually anyway. I care for my shoes and boots, and I don't abuse them. But I don't baby them, either.
I have a pair of very low profile bit loafers I wear as beaters. Low profile as in barely a heel, very casual, soft leather. Sort of a boat shoe that’s a bit loafer instead. They aren’t ideal beach day shoes but they are great vacation shoes I’ve ended up wearing on the beach many times. It’s probably awful for them but they still are going strong, although I had to really heavily moisturize them to stop some cracking early this spring and I got them resoled once or twice. I’ve had them for maybe 4 or 5 years. Anyway, a shoe like that would be a good bet for a beach wedding. It’s dressy in a casual, deconstructed way, you don’t baby it, it’s not at odds with the surroundings you put it in. Really, any kind of soft leather loafer at a price that doesn’t make you over-protective would work best I think if you have to wear a “nice” shoe on the beach.