We like mooring at Bitter End, renting a Hobie Cat in the afternoon, and having pizza in the evening at Crawl Pub.

If you haven't yet snorkeled over the Rhone, that's a fun activity.

If you are feeling really adventurous, you could do a discover scuba dive. Sounds like the girls are great in the water so I'd bet they'd take to it faster than you guys. This would take most of a day, since you would need to do a short lesson, shallow water practice, and then the real thing.