We go to OP almost every summer. I recommend Juno Beach Cafe for breakfast. The sunset view while eating dinner at the Sailfish marina is very nice. The food is good but not great but the view is worth it. We've had a couple of good meals at Paddy Mac's Irish Restaurant in Palm Beach Gardens. Cityplace in West Palm Beach is nice if it's not too hot. Lots of restaurants and shopping. At OP the burgers and chicken quesadillas at the tikki bar by the pool are good.
J Alexander's in PBG is a high end chain that imho make a good steak. Get the mac and cheese side. Shop at the Publix supermarket in PBG. Its right off the north end of the island and its nicer than the one on Blue Heron or Northlake. Get gelato at Gelato Grotto in PBG.
The Loggerhead Marine life Center is cool to see the rescued turtles. The McCarthy's Wildlife Sanctuary is great (bring a hat and lots of water) Call to reserve before you go since they allow only guided tours and its 30+ minutes away. The Sailfish marina Palm Beach water taxi give you a water front view of some of the Palm Beach homes.
If you drive thru Riviera Beach make sure you lock your doors. Avoid most of West Palm Beach except downtown and Cityplace. Don't stop on Blue Heron Blvd until you get to the bridge.
Be careful parking under the buildings, the garage is a little tight.