Early Lisbon Planning

Hi, I would make a few changes myself. Firstly renting a car for Sintra seems like a pain. There is a great train there, and parking is a challenge. Also Sintra has a lot of sites, the castles are crowded, but there are gardens and it is nice to walk around the town and even to the next town. Could you stay overnight in Sintra instead?
You could then head to Cascais on one of your other days. Again, there is a train, I wouldn't bother with a car at all for this trip.

I'm still making adjustments to my own Lisbon itinerary in October. One of those, based on forum recommendations, was to "stroll the Alfama at night, listening to Fado music playing in the background."

If you're arriving on Thursday from a transatlantic flight, driving on Friday wouldn't be high on my list. I don't like to drive within my first 2 or 3 days after an international arrival. The only time I did it was miserable.

Don’t drive to Sintra! Parking is awful and they have blocked off a number of streets making navigation difficult. Take the train from Rossio in Lisbon. It’s easy, less stressful and much less expensive than renting a car. You will need more than half a day unless you only want to visit one of the palaces. There are actually enough palaces to spend 2-3 days to see them all.
Cascais does make a nice day trip from Lisbon but I’m not certain you will have an extra day. If you do decide to come out here, there are several shops that your wife might enjoy and wandering around town is lovely. Unless you want a water view, our ‘yellow street’ has a number of fun restaurants. The concept was started during covid to help restaurants have more outside seating and it’s become a big hit. Casa da Guia also has several nice places with a sea view.

I would encourage you to spend the entire day in Alfama. Your trip looks pretty rushed to me and Portugal is all about slowing down, having 3 hour lunches and dinners. You will miss a lot of what is enjoyable if you rush too much.

Mini Bar is a very fun place for dinner. It’s one of José Avilez’ restaurants and a unique and delicious dinner. Ramiro is great for seafood but they don’t take reservations. There are so many great restaurants in Lisbon, you might google Culture Trip or Lisbon Lux. Even Time Out magazine will have recommendations.

You can't rent a car at 6 am unless you go out to the airport. You'd need half and hour at least for paperwork and checking the car and probably more than a few minutes to drop off the car. The best way to get from central Lisbon to the historic center of Sintra is by Uber or taxi and then take a tuktuk to Pena Palace (if that's on your radar). If not, you can walk to the other major sights from the center. You really need a full day to see the sights and even then you'll be rushed. Cascais is a nice 1/2 day trip from Lisbon but on another day.

We’re going to Portugal next year. Of the several food videos we’ve came across, we’ve found these two of particular interest. The one by Mark Wiens is from 2016 and the other from James Blick is from 2019. Both are still relevant though, in general, and in relation to some by others that are more recent.

https://m.youtube.com/watch?v=sLtuZEtCSLA

https://m.youtube.com/watch?v=V_yT5d97jBI