For the Pontevedra - Caldas de Reis stage, you might consider booking a room in Caldas de Reis (shipping your bags there) then walking from Pontevedra as far as the beautiful outdoor area of Barosa (
pics and more info here) and having a taxi from Caldas fetch you there and return you back the next day. Surely your hotel could give you taxi information or even arrange it for you, you'd just have to call someone when you were ready to be picked up. Also, there's a café right on the 550-N road at the entrance to the park where you can enjoy a breakfast coffee before starting the journey back to Caldas on the camino path (you do walk along the 550-N for a little bit right there).
From Pontevedra - Barosa is 15km (plus another .4 from the camino to the waterfall at Barosa). From Barosa to Caldas de Reis is a mere 6km. You could enjoy an easy, early day, especially since Caldas de Reis is known for its local spas (called "balnearios"). I found it so luxurious to be able to stay in a place for two nights - another perk of shorter stages and utilizing taxis!
Whichever way you choose, enjoy! Buen Camino!!