Yes, Snoopy Island is a gated complex.
There is only 1 bar/restaurant on the premises.
It caters primarily to boat (mega-yacht) crew.

Security at the Gate may (or may not) let you in if you say you are going to the restaurant (they don't want tourists going in just to gawk at the mega-yachts). They require a valid picture ID from every person in the car which they will take and return to you upon your departure, that is IF they let you in. I also know of people that they have turned away.

The restaurant itself isn't anything special, IMO.