vfinn,
I think I would break up my Cinque Terre visit into a couple days:
Day 1 -
- Train ride from Le Spezia to Monterosso;
- Go visit the old & new parts of the town;
- Enjoy lunch in Monterosso;
- From Monterosso - Hike to Vernazza, great hiking path that takes around 2 hours, going easily and enjoying the views;
- Visit Vernazza and then have dinner there;
- Take train back to La Spezia
Day 2 -
- Train ride from Le Spezia to Corniglia;
- visit Corniglia;
- Take a train or Hike from Corniglia to the next town : Manarola (this is a steep, challenging hike but most down hill - about 90 minutes);
- visit Manarola and then have lunch there;
- Take train from Manorola to the next town: Riomaggiore;
- Visit Riomaggiore and have dinner there;
- Take train back to La Spezia
The "activities" are discovering the people, places and food in all these towns along with the hiking and views. You can also swim in all of the towns with the best deep water swimming in Manarola. Monterosso and Riomaggiore have big public breaches I believe.
NOTE: The Blue Trail linking Monterosso - Vernazza - Corniglia. For those two trails you will need a Cinque Terre Trekking Card. All other trails are free!
Hope this helps.
Steve.