My wife and I have visited the Ile de Re many times over the past 25 years - usually for periods of 4 - 6 weeks at a time. I offer my thoughts.
The bridge toll is not as high as many people quote. Firstly, like the Severn bridge it is only payable one way - going on to the island. During the peak holiday season this is just under 20 euros for car and caravan. During the early season - which includes Juneit has in recent years been half that price. It was always said that once the tolls had paid for the bridge it would become free but many are concerned by what happened to Ile d'Oleron when this bridge became free. Therefore the tolls have remained and some of the income generated invested in the tremendous cycle track network. The booths are also, on occasions, used to turn back toursits who are not booked when the island is full to capacity, and also to lock the island down when there is an escape from the prison on the island - we have experienced this twice!
There is only one way to see the island - by bike. It is almost completely flat and cycling is an absolute pleasure. Nature lovers will enjoy the birds and flowers and the markets are all very interesting. My advice - stay near the middle of the island - use ACSI for the best deals, forget the car for the week and cycle. Is there enough to do? Since we have been retired we easily fill 6 weeks - we will be back again this year.
Whenever we meet people who ask what the island is like we say you will love it or hate it. Embrace the life style, expect no night life except cafes and restaurants, enjoy the wonderful artist's light, and see how many celebs you can spot. The island is also the destination for many Parisians. Our favourite coastal area of France. Enjoy but avoid August!!!!!