Sue.  
Don't miss Seville.  It is a beautiful city, and the trip includes what you could call a panoramic drive around some of the key points.  There are some awesome parks, and when we were dropped off there wasn't a lot of walking.  You end up at the Cathedral and there get your free time.  Lots of tapas bars, and time for souvenir shopping.  You can't get lost.  :thumbup:
There is also a chance to go on a short river cruise( for which you pay extra) but the walking in the central city area is flat and it's a good chance to pick up some souvenirs.  It's not a hectic city tour by any means.  
Just make sure to take a bottle of water with you.  🙂