10 Days In Portugal

Hi, we planned a 10 day Portugal trip in September for our honeymoon but I am worried that it became a bit rushed and squeezed.

Itinerary:

Day 1: Arrival to Porto at 10:00 AM, exploring the city.
Day 2: Douro Valley Wine Tour. All day. (Highly recommended so I decided to try it.)
Day 3: Porto to Lisbon with train (or flight. I couldn't figure out yet). Exploring the city.
Day 4: A day trip to Sintra, Cascais. (Maybe with a travel agency)
Days 5 – 9: Lisbon to Lagos with train. Hiking, kayak, cave exploring and Ilha de Tavira. We found a few tours and beaches around.

Day 10: Return to Lagos to Lisbon with train, then return home from Lisbon.

My fiancée wants to swim and spend time in beach but we also want to see Porto and Lisbon.

My biggest question is, is 5 days too much for Lagos? What else can we do in Algarve? Any beaches we can spend the whole day? Any highlights we should consider? Hotels you enjoyed! We are so interested in advice or Itinerary changes, good or bad! Thank you