That is a wise decision Sandy. although you will miss the attractive walk from Lisboa to the parque de Naçãoes in Moscavide .
I do not know when you fly back but there are interesting places on the CP which are worthwhile visiting an extra day.
Tomar with the Convento de Cristo. In 2013 we "forgot" to visit... Somebody on this forum told us we missed something so last year after our camino Ingles , we specially went back to Tomar to visit the Convento !
Coimbra. The medieval university with its famous library and the fado center with a nice musical fado show.
Porto.. Great place great food..great port wine...
When you are in Barcelos. Make a bus tour (public transport) to Braga A town with a beautifull-world heritage church -Bom Jesus do Monte- don't miss it
Santiago de Compostela.. Happy ending... The pilgrims mass...lounging..sightseeing.. Great time..
Other place are worthwhile seeing but here above are the highlites.
It look likes you walk long days 32 km or so but once leaving Barcelos after 18 kms there is
casa da Fernanda. Stop there is my advice and stay the night and you will understand who the Portugese are. Very kind people. Here you get the real caminho Portugues feel. Don't miss it !
Bom caminho