For a city with a party and drink reputation, Dublin is extremely family friendly. There are good activities and sights for children, and unlike in England, children are generally welcomed in appropriate bars and restaraunts.
The Guiness Tour, is a must see, and accordingly has a long line up to get in. The Temple Bar is a happy, lively (if touristy) nightlife centre.
Take a rain coat, and an umbrella; the weather can be extremely changeable.
Best Way To Get Around:
It is possible to walk around much of central Dublin, though the weather may force you to do otherwise. The hop on Hopff bus services are an entertaining way to take in the sights and get around.