Walker Bays are not fiberglass. They are injection molded high density polyethylene, pigment loaded which affords UV protection.
I know several people with them and maybe not the greatest rowers, but decent as the owners did row them , are adequate and should be well within your needs as described. They were very happy with them as they were far better than the alternatives.
Beach them on the rocks or barnies and they will get marked as will any boat. But they are tough and will withstand that. Any damage will be cosmetic.
I looked at the site and the 8' is 71 lbs. or so they say.
Walker Bay
As for rocks any boat is going to suffer. I have a a fiberglass Livingston and beach it when needed. Granted I don't like it but I also don't fuss either as it is the only dinghy we have and if we wish to go ashore then there isn't much choice.
Aluminum would be good too but most of the ones I see are larger intended for fishing applications so at least 12' +.
FWIW.