Also, even if you got to the Beach House, it requires a room key to get access inside.
Finally, as I understand it, the use of the Beach House is meant for members actually staying on points at the time. This is similar to the pools at OKW and BWV are for use by members staying on points at the time, and not for members in general who are just in the area.
If you just want to see the Beach House and the resort (assuming you've never been there), you can probably arrange that with the HH sales staff.
There is an RV resort on Hilton Head Island, although we've never used it. Forget about driving a large motorhome anywhere. It just isn't practical. From the post above KMarie couldn't even get their class B unit in. A class A or a class C unit definitely would not be allowed in.
If you stay in the campground and have a toad then you could use it. Another choice, if you don't want to stay, is park your rig at one of the Outlet malls parking lots before you get to the island, then use your toad vehicle to drive around HHI itself.