I live here (just!!!), we are moving back to UK in August. For work reasons, would have loved to have stayed a bit more. I have a different experience because my husband is portuguese, but am still very much a foreigner.
In short, the north outside porto is very very rural. No one will speak much english, and you may have problems adapting and fitting in. There are international schools in Porto, notably CLIP (I think that is the name), and I would imagine that to feel comfortable quickly unless you are a linguist, you would be better being near Porto or Cascais/Lisbon.
That said, I would definitely recommend the north over the south, just from a cultural point of view - once you start hitting algarveland, all hint of the true portugal disappears.
We live near Cascais, which has a nice balance. It is quite touristy in the summer, although nothing compared to the Algarve. Good schools, both international (there are 2 English, 1 american, 1 german and the french school in Lisbon). The area is safe (as is most of portugal) and very child friendly - nice creches and play areas, clean beaches and some great parks that far surpass any you will find in the UK. Healthcare is good, if you are prepared to pay for it, or have insurance. The public system is good in emergencies, but not for general health. There is a fabulous english GP that practises in Cascais, as well as an international clinic. A consultation would be about 60 euros if you paid privately, with insurance only 10 euros.
The portuguese people are great, whether you are a tourist or permanent. WE have only ever been met with kindness, courtesy and patience at my terrible portuguese. It is very child friendly pretty much wherever you go, apart from dodgy pavements for buggies! Also, in busier places, someone somewhere will speak English. The language is notoriously difficult.
It is a great country, we have been here 3 years and loved every minute, the only thing that could be difficult would be finding a job. Also, they are nearly as bad as the french when it comes to beauracracy and paperwork, so be prepared for a long haul if you want to become residents/buy a house/open a bank account/start a business etc......
Good starting point may be the IWP, International Women of Portugal. Lots of info and contacts, should be able to find it on google.
Can“t think of anything else to add generally, if you want more info, let me know!