Portugal itinerary Porto to FAO - trains question

Considering traveling for a destination wedding in Douro Valley and flying from the US into Porto then doing a train from Porto to Lisbon with a day or two in Lisbon then a train from Lisbon to Faro for 4-5 days in Algarve.

Thoughts on doing those trains vs just flying Porto to FAO? Figure with security lines / boarding etc time is similar. Is it comfortable on train? Is there room for my luggage?

I’ll have my family including toddler with me. We did a similar train travel before in italy for context and found those trains comfortable enough.

I’d need to fly home from Lisbon to US to fly direct so alternatively I could see Lisbon on the way back via train or consider a car service but that could get costly. I’m not comfortable driving.