I live in Porto and it is a wonderful city. I can recommend Angel’s Share a cocktail bar across the river in Gaia. It has the best view of Porto. Mind the glass in Cedofeita is lovely wine bar, go towards the back as the room is more lounge like at the rear. Octant Douro is a beautiful hotel in the wine region. From Porto a trip to Foz on the coast via the old tramway is a must. Lots of lovely restaurants there especially Cafeina and Al Mare right on the coast. A short trip on the train to Braga is highly recommended, a beautiful city.
Back in Porto a visit to Bolhao market, great produce and you can wander round with a glass of wine from one of the market stalls. A good range of restaurants to eat at on the second floor too. You can rent a private boat for 2 or 4 hours on the Douro, we have used Douro boatman (see trip advisor reviews) you can take your own drinks and picnic lunch and choose your journey, prices around 200 euros for 4 hours for the boat. So much to do I could go on and on.