Paul
I cannot imagine those on the RIOW race will be going on the sands. They will be too exhausted to bother (Though I may be wrong).
In any case, it would be even further to walk to the dinner (though you say you are not going to eat with the rest).
For the Bembridge rally we eat in the Bembridge Sailing Club. Also near the beach there is a pub called the Pilot Boat Inn, but as you say, you are not kitted out for beaching the boat.
I don't know where dinner has been arranged, but on the assumption that it is not the Beach Cafe, this would be an option for you. The food is quite good there (you may even buy fish and chips). To get there you walk ashore from the pontoons and strike off NE (about 10 minutes walk). The Cafe overlooks the Solent and you can see it as you approach the final narrow entrance to the harbour.
Centre of this picture.
By the way - note the channel into the harbour.
Regards
Don Harvey
Web Master
Parker 325 'Calypso'