We did most of the ports on our own. I do have a few suggestions though. In Gibraltar, if you want to do a rock tour and see the monkeys, there are plenty of vans waiting as you get off the ship to drive you up for much cheaper than the Disney excursion. There will be vans right outside the terminal, but walk a little ways past the gates, and the price drops $5.00 per person. We took the tour for four of us for 80 euros. Also, with Disney you take the tram up, which sounds fun, but it is a mixed bag. There was about an hour wait to get on the tram and when you get to the top there is A LOT of walking if you want to see everything. With the van tours, they drive you to each spot and stop and wait for you. They will take you to St. Michaels cave, a lookout spot where you see Africa, the top where there are lots of monkeys and the battle seige tunnels, which we missed because we spent too much time monkeying around

This was by far our favorite port and I highly recommend doing the tour. Afterward, they dropped us off in town and there is a nice street which is pedestrian only with tons of shops and pubs. We loved it. You are able to walk from the town back to the ship, although it is a bit of a way,it is very doable.
In Cadiz we did the Jerez tour to go see the horses. I read some reviews that did not like it, but my family enjoyed it. If you have any appreciation of how difficult it is to train animals, you will be amazed at the steps the horses do. I am not sure what the rest of the tour will entail on the WB, we had a tapas lunch at a lovely winery after the show. We also thought that was great, although some others did not. I guess it just depends on what you like. After dinner on the ship, and the kids in Oceaneer Lab, my husband and I walked around the ocean side of the city where the old city wall is. It is absolutely gorgeous. There were beautiful gardens everywhere and the sun was setting, very romantic.
We were disappointed in Tenerife, but I think it was because we did not plan anything. All the excursions were so expensive I did not book any,and when I realized that none of the cab drivers spoke english, we were hesitant to let them take us on a tour they try to describe by pointing to a map. There is a city you can walk to from the ship,but it is really a city, and not a beautiful one like Cadiz or Barcelona. We ended back up on the ship about 1pm, which was fine because it was the only day on board I got a tan!
Hope this helps. Feel free to ask any more specific questions.