Tramore could be a nice option. Its about 20 min drive from Waterford city and has lovely beach, swimming pool (splashworld), amusements, arcades etc. Some lovely restaurants in Tramore also.
Its close to Waterford so its easy to go to town for a better choice of pub grub/restaurants, shopping, day trips to Dunmore etc.
Choice of mobile homes / renting a house.
We rented a 3 bed house in St Helens in Rosslare for a week in June. It's a large very well spread-out estate of houses (gated community) about 2 miles outside Rosslare on the St Helens Golfcourse. It's about a 10 minute walk to a huge and very quiet beach at the back of the golfcourse. Ideal is the kids are happy swimming and messing on the beach or if anyone is into golf.
We had some relatives stay in the holiday villas a few years back while visiting us and they loved it. Plenty of beaches within walking distance ( would recommend Ballinesker over Curracloe beach) Have never tried the on site restaurant but have heard good things about it. You also have the Hotel Curracloe nearby which does good food, plus it's only around 15-20 mins drive to Wexford Town.
The Ferrybank swimming pool has just reopened after refubishment and is would only be 10 minutes drive for you, it's just behind the Riverbank Hotel, just off Wexford Bridge.
Four of us are heading to Tramore this month for 4 nights. A two bedroomed house with garden, close to the beach is costing €350 for 4 nights. Just google holiday home let in either Wexford or Waterford and you will get some good deals. Tramore has plenty to offer as previously posted if you dont feel like taking the car or want a few drinks locally. It is also a short drive to Waterford, Dunmore etc.
Was in Roslaire Strand earlier this year and loved it, hope to get back again around October. Much quieter than Tramore though so used the car a good bit.