I joined up with Kilcoole about 6/7 weeks ago and find it great. I only do the Monday sessions on the track but there is another one during the week. There is also a kids session on at the same time that is well organised and has plenty of youngsters at it. There are a few of the Wicklow guys who are also in Kilcoole.
My nephew is with Greystones AC and they seem to have a great set up for teenagers - there is a good group of them at a good level so they must be doing something right. Not sure how they are with smaller children or what their adult set up is like.