Is it difficult to navigate from the airports to the train stations to use the high speed train for travel between Lisbon and Porto? We will have a backpack and a checked bag to tote as well.
Both airports have a direct metro line to the main train station.
Lisbon's airport website has the details, but you have to google Porto train station to airport to get the details.
From Lisbon airport take the Metro Red line to Lisbon Oriente train station , at Oriente take the AP(faster) or IC(slower) train to Porto Campanha.
From Porto Campanha take the Metro E line, the last stop is the Porto airport.