I ended up just going to Gib. Really liked it, even though heights are a huge phobia of mine, so I didn't go across the highest road from the Skywalk to the northern part of the Rock (got to the Skywalk, took one peek below and retreated to the lower roads). The one thing I was disappointed about was the lack of flights to the airport on the day, so I couldn't take any photos of the planes landing or taking off, but it was a rather minor disappointment, if I'm being honest. Doing Tangier in the same day would definitely not have been advisable - I was properly wiped out after the three-hour hike. Their botanical garden and tiny zoo were also well worth an hour's detour.