You'll find at the house a varied documentation (and up to date) which will allow you to program your walks.
Some suggestions :
In 300m, the beach, the ocean and the sailing school. In clear weather, you will see Houat and Hoedic islands.
You can swim and also, at low tide go fishing on foot on rocks of the wild oysters (tool at home).
Port Crouesty, in 10 km (at the end of peninsula) proposes a casino and many shops.
Visit the castle of Suscinio (possible on foot by the beach and the forest).
Between the gulf and the ocean, landscapes are very different, but everything is close.
From Port Navalo (near Port Crouesty and Arzon), boat ride over the gulf or to the Ponant islands : Belle-île, Houat and Hoedic.
Take a walk trough the medieval lanes of Vannes.
Merlin the magician and the fairy Viviane are waiting for you in Brocéliande forest about 50 km (direction Rennes).
Discover the sea birds by participating in the (free) walks organized by L.P.O (French bird life) of Morbihan.
Do you like megaliths? The visit at Karnak is expensive, discover Erdeven and picnic in the forest near a dolmen.
To help you in you choice, consult the necessary website schedule of tides (paper at home).