I would add more nights to Lisbon. Two nights really gives you one full day and part of another day. As a reference point, we spent 5 nights in Lisbon, and that included a day trip to Sintra. There were still a few things we didn't see in Lisbon. Are you planning on going to Sintra? If not, I highly recommend spending at least one day in Sintra.
What are your interests? For example, in Lisbon, we visited the following: Gulbenkian Museum (one of our highlights), Sao Jorge Castle and then slowly strolled through the Alfama (our favorite day); spent a day in Belem visiting the Jeronimos Monastery, Discoveries Monument, lunch, and then Coach Museum. Visited Sao Roque Church and Mosteiro De Sao Vicente De Fora. And wandered through the other neighborhoods and stopped at some miradouros (viewpoints). I would feel very frustrated with only 2 nights in Lisbon.
We only had time for Lisbon on this visit so can't comment on the other places.
We were in Lisbon last April, towards the end of the month. Weather was perfect for sightseeing, sunny and 70's. So it will be a tad warmer when you are there (probably in the 80's). There are websites where you can check historical weather data.
if you like seafood, I highly recommend Cervejaria Ramiro, recommended by the late Anthony Bourdain. It was our favorite meal of the trip. You can stop at the Time Out Market, a huge market hall with tons of food stalls and small restaurants. We had delicious seafood at Monte Mar at the Time Out.
We stayed at the Hotel Real Palacio, Rua Tomas Ribeiro, 115, near Edward VII park. We were very happy with our hotel. Large room and storage space; price included a great breakfast buffet. It's not in the city center, though, so might be too far for some people. We did walk down Avenue Liberdade a few times to get to Rossio and Praca do Comercio. About a 20 minute walk. Price was $170. We took taxis a lot because I have some mobility issues due to arthritis. Taxis are inexpensive and plentiful.