Stayed as part of a group of 10 (8 addults and two young children). Quinta de Sao Bento is an excellent villa - the building itself is great, the two barbecue areas and swimming pool are excellent, and it's just a 5 minute walk into Prado, which has just about got everything you really need, or a 10-15 minute drive into Braga. Porto is a 45 minute drive away.
Dona Rosa and Manuel live on the grounds if you need any help; I would highly recommend having Dona Rosa cook an authentic Portuguese family meal for your group, and if you happen to run into trouble (as I did with a car break down) Manuel has just enough English to help you deal with the locals,.
If you want a base to explore Northern Portugal then you will struggle to do better than this!