The whole area is good. There are a lot of places to stay - for example the houses on the harbour used to be available for holiday rental (or at least they were 30 years ago) (there is one on Air BnB). https://www.airbnb.co.uk/rooms/7235371 (The houses were upside down with the accommodation on the ground floor and the living space on the first flood so you got a good view across the harbour). It depends how large your family is - there are things like self-catering cottages in the area which are also good bases (nice if you like the countryside) outside of Port. The area is good for FR, WHR but you also have WHHR, Llanberis, Snowdon and Bala all within pretty easy reach. TR and Fairbourne are accessible by train from Port.