I did large paper lanterns with hanging LED lights, I bought them from Asian Ideas (online store) 16" and bought 14 of them which I think was enough. I also brought wooden bowls that I filled with sand, white pillar candles and faux orchids and brought orange table runners. I brought pink chair ties too which looked good. Another thing I brought was small white bags (similiar to the above photo) that I got from Micheals and punched out the rim and filled them with sand and fake tea lights and put them on the rim around the restaurant.
Once I have pics I will post. I am selling my lanterns, table runners, and chair ties soon too.
Ps re: the min number for private bookings I think they are flexible about the numbers you should be good to rent it with >25, they just don't want to close the place down for only 10 ppl
pps: there are no good shells on the beach so don't count on picking them up there!