Also agree with Tenby and surrounding areas. We go every year and love it.
Folly Farm is great for kids. There's a farm, zoo, old fashioned funfair and huge indoor and outdoor play areas. It's a great day out. Oakwood is good too but I wouldn't pay full price - if you shop at Tesco, you can use Clubcard vouchers via the boost thing to get entry to Oakwood and Folly Farm. We went in August last year and the longest queue at Oakwood was about 20 mins. Most rides you can get on straight away.
Lots of castles to visit near there - Pembroke Castle often does reenactment days which the kids can get involved in.
The beaches in Tenby are fabulous too.
Bluestone is good for swimming - you can use the pool even if you're not staying at the resort, though you have to book in advance and it's quite pricey, although I think they're 3 hour sessions. There's flumes, a wave machine and a lazy river that goes outside.
The dinosaur park is quite good too - although yours might be a bit old for it. There's lots of rides/things to do, all included in the entrance price.
There's Heatherton (no entrance fee but expensive for rides etc and has many the same as the dinosaur park). Also Manor Park wildlife park which is not a bad day out. You can go in with the wallabies and feed them.
Can't really help with food as mine are little and don't eat out much; we tend to take picnics for lunch. We've always had good food and great service at Qube in Tenby.
Can you tell I love that part of the world?!