Looking for ideas of where to go / base ourselves on a trip to Northern Portugal in August. We will have a few days in Porto itself but then will have another 6 days and not sure where to go? DC's are 13 and 10. They like beaches / pools but also happy to walk and explore / sights etc too. Can anyone offer any tips of locations to look into? I haven't booked the return flight yet so potentially could return from Lisbon or Porto. Looking to spend 8-10 days there in total including the Porto bit.