French Riviera by Emilie
The Lérins Islands: choose Sainte-Marguerite or Saint-Honorat for the day
Before booking the boat, decide what you would like to do once you reach the island. On Sainte-Marguerite, I suggest the woods, the Fort Royal and a stop to watch the birds. On Saint-Honorat, the walk centres on the abbey, the vines and the shore. For a first outing from Cannes, give the day to just one island. You will have time to settle into it, with a picnic or lunch included.

Sainte-Marguerite, with binoculars and a picnic
The Fort Royal gives the walk its first destination. The story of the Man in the Iron Mask, imprisoned here, may interest children before you even arrive. If you would like to visit the museum, check its hours before choosing a boat, so you have enough time ashore.
Leave time for the Batéguier pond as well. Its observation point lets you watch birds without approaching the banks. The birds change with the seasons: binoculars and a few quiet minutes are more useful than looking for one particular species.
I recommend bringing lunch and water. You can then stop along the way according to the route you take and when everyone gets hungry. The island map will help you link the fort, pond and woodland paths. There is no need to plan a full circuit with young children.
If you mainly want to be beside the sea, give yourselves that time and leave the fort for another crossing. From a home in Cannes or nearby, the islands can become several different outings over successive stays.
Saint-Honorat: vines and an abbey facing the sea
On Saint-Honorat, the rows of vines are as much part of the landscape as the abbey buildings. The monks make wines and liqueurs, and their shop is a way to discover that work. You are walking through a place where a community still lives, with its own spaces and daily rhythm.
Walk around the abbey and look at the fortified monastery rising beside the water. If you would like to enter the buildings open to visitors, check the abbey's visiting conditions before leaving. Dress appropriately for the church and respect private areas.
For a restaurant lunch, La Tonnelle is close to the landing stage. Book your table while checking the return boats too. You can then enjoy lunch without calculating after every course how long you have to get back to the quay. It is one possible plan, not a requirement: a walk and a stop you have prepared yourselves can fill the day just as well.
Check the return boat before leaving Cannes
Several companies serve Sainte-Marguerite from Quai Laubeuf; Planaria sails to Saint-Honorat. Check the island named on your ticket carefully. There is no direct shuttle between the two: travelling from one to the other on these services means returning to Cannes.
Note your return departure before boarding and allow time to reach the boat. In autumn, a jacket in your bag is useful for the crossing. In strong winds or if services are disrupted, save the islands for another day and choose a morning in Cannes instead.
On the islands, take your rubbish away, keep to the paths and leave plants unpicked. You explore on foot; good shoes make it easier to alternate between woodland trails and stretches near the shore.