We have just been to Three Cliffs Caravan site near Swansea and can highly recommend it.
The sea view pitches are more expensive but the view of the cove and beach is stunning.
Newly refurbed shower blocks (lots of them so never a problem to a shower when you want one) are super, it is kept immaculate and there is a nice shop on site which sells all the essentials and great local produce (cakes are amazing) !
Its about a half mile walk down (bit steep in places) to the lovely sandy beach which is dog friendly all year round.
Staff there all very friendly and welcoming and they are more than happy to recommend places to visit or eat or advise on local walks.
Just a couple of miles along the road there is also Oxwich beach which has a car park (ยฃ4 charge) right next to the beach ideal for families with small kids who want to take a picnic and spend the day.