We made ressies early for the Dolphin encounter (June 25th cruise) and it did sell out. I'm not sure about the concierge having available excursion ressies but I know for a fact that they hold stuff aboard the ship. We were in Cat 3 on the June 25th cruise and when we met with the concierge, she took us down a whole list of things (some we hadn't even known about) like the wine tastings, bridge tour, tea with Wendy, hair braiding, etc. We were able to switch our Palo time, the kids club representative came to us to give us the pager, and we basically named our times for the other events. I'm sure they will go out of their way to help you guys out...especially with so many of you at conciege level. But I do know that, even if you're not concierge, not all the shipboard ressies are released prior to the cruise because some people don't have (or use) online access and they'd really be left out otherwise!
CB