(Edited based on replies. This is a work in progress and thanks to all)
Hi all, I have done my research but still need some help from those of you who have been there. Thanks in advance.
Flying in and out of Porto. Land at 3:30 pm. Out at 5:30 am ( yes, cheap ticket).
We want to take it a bit slow, and I would prefer a minimum of two nights at any location. I would be happy just to hang out and walk around a city, hitting cafes and restaurants and people watch. We have a child so we are not hugely into churches or museums at this point. That being said, we most likely will visit some must see landmarks. We also don’t have to see the beach on this trip.
I plan on taking the train whenever possible. Our first time here and these three locations look interesting, and we can split the nights among the locations:
Porto: 4 nights upon arrival. Relax, walk around the city, Mercado do Bolhão.
Pinhao: travel by the train from Porto, 3 nights. Visit wineries, boat cruise, maybe take the train to the very end of the line as a day trip.
Coimbra: travel by train from Pinhao. 2 nights. 
Visit the university, library, etc.
Lisbon: travel by train from Pinhao, 5 nights. Take day trips from Lisbon.
Porto: travel by train from Lisbon. 1 night at airport hotel
We are not against renting a car for a portion of the trip if it is significantly more efficient (saving 4 hours or more).
Does this plan sound reasonable? Any suggestions?
Thanks.