Hi Talfont. I'm actually from mauritius and there are many things to do in mauritius. Yes do get a car and drive around as it is much easier. There are some traffic but mainly in Port Louis (capital) just like every other main cities around the world. You have peak and off peak traffic.
It's not all about beaches, only tourists who have not done there research before getting there but once you venture out of your comfort zone (resort) see below. These are just some highlights
Port Louis - the grand bazaar, Caudan Waterfront / shopping arcades, museums- view the oldest stamp(s) issued in the british empire apart from GB , visit the second oldest racecourse in the world, the parliament house, panoramic view of the city from La Citadelle, botanical garden-one of the oldest in the world to name a few.
However around the island you can visit -
Chamarel for the seven different coloured earth and waterfall
Casela Nature Park for its collectins of birds around the world , giant tortoises, zebras, tigers/lions where you can walk with them, hire buggies or quad bikes and tour the park and see animals and pat them, like as if you are on mainland africa.
Le Morne - Great beach and mountain background,
UNESCO World Heritage List
Grand Port - south east of island, dutch ruins, oldest settlement in mauritius before the french arrived and witness ruins excavations.
Cap Malheureux - northern tip of mauritius
Curepipe - visit trou aux cerf- extinct volcano and panoramic view of the town and part of the island.
For beaches take your pick but do see at least 4 of them on all 4x side of the island as they are all different in terms of temp water, colour, the surroundings. You can feed dolphins, deep-sea fishing/marlin, scuba diving- good marine life, rock or mountain climbing- average 2 to 4 hours to climb pending your fitness or take a helicopter there, eat as many fresh fruit and vegetables as you can due to the rich volcanic soil.
Info available at travel agents, book shops, internet, take your pick.
Enjoy