Waitingforgodot:
For kids I would say these are some of the best places to visit:
Environmental adventure playground There's a rainforest and galaxy and quite a few other things!
This is the Dublin alternative of The London Duck tour, which I've taken with my DSDs many times. I've never taken the Dublin one, but the London one is great fun - even if you don't listen to the educational stuff and just wave at people out of the windows!!
THis puppet theatre is good, if your kids like stuff like that!!!
There is, of course, Dublin zoo... Pretty standard as zoos go.
There's Trinity college, but not really sure how much that would hold the younger kids attention!! And the Guiness store - but again, can't say what this is like from a kids perspective.
day trip on the DART to Hoath is nice and equally you can take the DART the other way to Dun Laoghaire, Dalkey and Killiney... Dalkey Hill is nice to climb if your kids are outdoorsy sorts and the views are gorgeous!!
Slightly further afield, but still do-able is Avoca or WIcklow - Glendalough is lovely and POwerscourt is a favorite place of mine.
Hope that's of some help!