If we plan on spending days at the beach while in Barbados, St. Lucia, etc. are there places where we can rent lounges or should we bring beach blankets, etc. with us. Are there some beaches with umbrella rentals? Does Princess offer excursions with these amenities? We would definitely be willing to pay for lounges and umbrellas at the beach.
No need to bring beach blankets, you can get towels from the ship before your excersion, just let the cabin stewart know that you will be needing them. When you get back, just leave the dirty ones in the cabin and the stewart will replace them with clean ones.
Been to a few beaches and it was very easy to rent a lounge for the day, just depends on the exact beach, but you shouldn't find that to be a problem.
The purser's desk is always a good source of information on the best local beaches. The staff themselves head for the beach each time the ship is in port. Just ask which one they personally like the best.