Well if you are spending the day at the BL and you have time, the LAVA restaurant is perfect. We had lunch here in our BL bathrobes and it was nice and cosy seeing as it was snowing/hailstoning/sunny outside. All of the windows are glass so you can see outside while you are eating and the roof of the restaurant has a great view over the lagoon.
We were there in March, I dont remember a buffet as we ordered from the menu. Food was good and the place is very elegant but you dont look out of place in your bathrobe.
It is a bit pricey but hey you will probably only go to the Blue Lagoon once if your life so why not make the most of it!
If you own or manage Lava Restaurant, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.