My family (2 pre-teens) and I will be taking 2 separate day trips to Sintra by uber from Cascais. One will be on a tuk tuk tour with Yes You Deserve! (I know, touristy...but great reviews and I think the kids will love the ride and save our legs!). A separate day we'll uber again and visit the spots we didn't before. The tour will allow 2 monument inside visits and 2 other activities (including coastal stops...we've chosen Peninha Sanctuary and Azenhas do Mar as those stops), lunch in Colares and will drop us in Cascais.
My thought would be for guidance and logistics, to include Montserrate on the tour. Should the other be Pena or Regaleira? For reference, we aren't as much interested in touring Pena inside but it being up the mountain and the logistics, I wonder if the tuk tuk would best be suited for it. The other dilemma is the Moorish Castle...I think the kids would love climbing on the walls and it seems to pair well with Pena. Should we do Monserrate/Pena with tuk tuk or Regaleira/Monserrate with tuk tuk? On the second day by ourselves, we'll want to stroll the town and pop into the National Palace after lunch. Would Regaleira be best suited with that since it is right there and flat? Then we'd have to make our way to Moorish as well. How would you best fit these together for best optimization and energy saving? Thanks!
In April we took an uber to Sintra for a day. We purchased Park de Pena tickets in advance for the terraces and grounds. Our uber driver took us to the Pena Palace entrance just before the gate opened. We did not feel it was necessary to see the inside of the Pena Palace and we were able to bypass the long lines for the palace interior. We loved the views from the terraces and walked the palace walls and saw the Moorish Castle in the distance as well as forests and hills and views to Lisbon. We entered a small Chapel and also sat outside at the Pena Palace Cafe with lovely views..
Afterwards we went down to the Main Pena Entrance gate and called an Uber to take us to the Monserrate Palace. When we were there the exterior was under scaffolding and reconstruction, but the interior was beautiful and intricate. The ornate grillwork and ceilings were amazing. The grounds and the cafe in the gardens at the Monserrate Palace were great.
We did not go to the other locations that you mentioned, so I cannot comment on those.
I think you will really enjoy your time in Sintra.