Based on your necessities, I don't know if the Riu is the right place to have your ceremony and reception. It is not on a swimmable beach, and the water isn't totally bright blue. I have a feeling the gazebo is pretty private, as I didn't see it when I was staying at the Riu last October, but this was before I was engaged so I wasn't totally paying attention to that stuff
I'm doing what sassybride is doing - we are all staying at the Riu all week as it's a really fun resort and is a great place to vacation, but I'm having the ceremony and reception off-site. I think you might want to look into this if you're feeling uneasy...