If you plan to spend 3 days in Lisbon, get the 72-hour travelcard for the trains (doesn't work on buses or trams) so you can get into and out of the city easily. The trains are frequent (30-40 mins, depending on whether it's a limited [rush hours] or a local [other times])

kayaking in cascais (November should be good for kayaking - I do sailing year round). See if there are other kayaking places. There are also tons of surfing schools along the coast if you want to learn or just rent a board.

Guided tours - maybe a walking tour in Lisbon.