For stunning white sandy beaches you should look at North East side of the island. There you have several 5-star resorts with varying flavour. Some pure romance, some more active and some more aimed at families.

http://maps.google.com/maps?f=q&hl=e...9,0.173035&t=h

We go to a resort called Beau Rivage as we usually are a big group, with some children. I like it very much. Great hospitality, good food, excellent activites and if you really feel like you don't have do a thing

I recommend Mauritius very much. Especially the better resorts.