I think this is ambitious.
Sintra is a whole day between the palace, the old Moorish castle walls, and Quinta de Regaleira (which is also a must see). Honestly we felt like we could have used an overnight just in Sintra. (You could combine Sintra and Cascais).
I don’t think you need two nights in Aveira unless you are using it as a home base.
Leave time in Porto to visit the Douro Valley (can do on a boat) and going to tastings in the port houses.
PS. A number of things were shared in this recent thread that may be helpful: Also looking for suggestions for Spain and Portugal