Hi Tartangal,
We are considering that cruise for the fall west bound trip. We have made the trans-Atlantic crossing several times, and really enjoy the mix of sea days and ports of call, and they have an interesting itinerary. We have also sailed, and loved, the Millennium class ships but haven't sailed on Celebrity's smaller ships yet. There are several recent reviews available for the Galaxy that might help you. Your flight planning may take some work to get what you need. With a repositioning cruise you are going to need an open jaw flight, and it is always best to check out the Celebrity air sea package first. Most air carriers don't price an open jaw flight as a round trip, but charge for two one way flights (usually like two round trips). When you get your Celebrity air charges you shoukl note that it will include the ground transfers, which are considerable for both Galveston and Rome. Houston International to Galveston and Civtavecchia to Rome, are about 2 1/2 hour transfer. If your decide to use an air deviation and the Celebrity air sea package you may want to stay in Houston and use the ground transfer to Galveston. For the Venice extension you can still use an air deviation to change the return flight date. For the Rome to Venice flight I have flown with Volare Air, which is a low cost Italian air carrier that had newer aircraft and good service.
Regarding shore excursions we have found that Key West, Madeira, Gibraltor and Nice are all very easy to handle on your own. It is best to first check Celebrity's internet site, to see what you might want to visit then decide if you can want to arrange things for yourself. The rail station in Nice is easily accessable and you can travel on your own to Monte Carlo if you like, and both cities are easy to get around if you get a good map. I found that it is better to do Gibraltor on your own as you can easily walk the city at your own pace, and take the funicular indidually to the caves etc. Your should have a great time on this cruise with lots of variety, and the weather should be good at this time of the year.
Peter