Bryn Derwen is in Llanfair, just outside Harlech in North Wales. It's a modern house, recently done up. Sleeps six, three bedrooms, one bathroom.
The main thing is the view. The garden looks straight out to sea. It's a good size, with a seating area and space for kids to run around.
You're two minutes in the car from Llandanwg beach. It's sandy, good for buckets and spades, or fishing off the shore. There's a cafe in the dunes if you need a bacon sandwich.
Harlech village is about a mile away. It's got the castle, pubs, shops, and a fantastic beach. The castle is a Cadw site, part of the World Heritage stuff. The high street there is very steep, if that's of interest.
Right on the doorstep, you can walk to Llanfair Slate Caverns and Farm Park. For golf, Royal St David's is in Harlech. The train station is there too, on the Cambrian Coast line. You can get the train to Barmouth or up to Porthmadog without using the car.
Within half an hour you can drive to plenty. Porthmadog has the Ffestiniog Railway. Portmeirion is a strange and interesting place to wander round. Up in Blaenau Ffestiniog, there's Zipworld and Bounce Below if you're after something active.
The house has parking, a dishwasher, washing machine, WiFi, and a TV. Bedding and towels are included. One well-behaved dog is allowed.
For planning days out, these sites are useful: Visit Wales and National Trust Wales.