Sitges, I lived there for 9 months when I worked in Barcelona. I wouldn’t recommend it to a family with two young kids though. The place is geared up to coping with the masses escaping Barca and gay nightlife. It’s east coast and unpleasantly hot most of the Summer, my view is perhaps coloured by living in SW France and wanting somewhere cooler than home rather than hotter.
Spain’s north coast gets a few dull days in a Summer week and it even rains now and then. It’s where a lot of people from Madrid head for on holiday in search of a sea breeze. Beware of campsites, some are good but many are my idea of holiday hell. Overcrowded, noisy, smelly. Alberge, hotels and casa rural are a better bet. booking.com is where Madame hunts for the places we stay.
You don’t want to stay here, promise. Somewhere not far west of Gijon, I can’t remember where exactly but the “sand” was black stuff dumped in the sea my the mining and steel industry.