We have been to Ile de Re many times and Oberon a couple of times but much prefer Re. Would go as far as saying that Re is one of our favourite places in France. The cycling routes on Re are superb, this being our mode of transport when we park up. The site off the roundabout at the start of Rivedoux Plage is an ACSI site and has an aire at the entrance, but we tend to go onto the site as with reduced rates it’s about the same price. From there we can cover the whole island and also bike into La Rochelle with a good cycleway over the bridge. I once cycled over the bridge with a spare bike at the side of me, to the airport, to meet my daughter who was going to have a week with us! The toll for the bridge, assuming that it is still the same, has a low and high season price with the change in mid June (I think- date should be able to determined via Google).
Our last visit, two years ago, we thought we would go to the aire at the very end of the road though Les Porter en Re (farthest point from the bridge) so drove straight there only to find the last place being taken by the motorhome in front of us. Had to drive all way back to Rivedoux. Two days later I biked to this aire and found it completely empty! We have also stayed at St. Martin, but prefer Rivedoux site for close proximity to beach (I also take a blow up kayak) and La Rochelle.