Crag cave just outside Castleisland is fantastic for adults and kids- it has the caves which are just as good as Alliwee but it also has this huge soft play area for young children- with a cafe right inside so that you can sit down, have a coffee and read the paper while the kids run around up and down bouncy castles, big slides, etc etc Theres also an outdoor play area and a bigger restaurant too for lunch. I would really recommend it especially for the younger children. I was there a couple of days ago and they said they are open every day this year until christmas.
The Killimer- Tarbert ferry in itself is always a winner with kids. If you're lucky you might even see a dolphin/s.
Killarney is great cos there are loads of walks all over the national park- possibly best to plan in advance what walks to do by buying a book and bringing a picnic. You can go out on boat tours around the lakes ( don't feed the gondolas!) and go horse riding too. Or take the jaunting car ride around Muckross.
Killarney town itself is incredibly busy and a little pricey but scenery is great and if you bring a picnic then you're sorted.
Tralee would be a good base for a few days around Kerry- it's central enough to do lots of day trips and has some attractions of its own- the Town hall has a museum, theres the Aquadome and lots of beaches around.
Must admit I love Dingle any time of year. Nice town, lots of restaurants that will appeal to children and adults, theres the aquarium and boat rides and then the stunning scenery around Slea Head. Well worth a trip.
Having said all of that if they are in Clare to begin with, how about a trip to the Aran islands? I love it there- although I think a couple of days would be enough.