There is an activities section on Mumstown (see the toolbar above) with some suggestions, here is the link to that: http://www.mumstown.ie/activities/
Aside from that, here are some ideas:
Board games – Junior scrabble etc are good fun
Baking – you can buy easy to make cupcakes & brownies and then get different toppings, like the Dr Oetker range, to decorate them
Colouring / painting – Get a plastic tablecloth (available in most euro shops) and let them at the table with colours & paints. The tablecloth can be wiped down & reused or thrown out.
DVD’s – Its nice to snuggle up with a DVD on a rainy afternoon.
Sky TV recordings – I keep an eye on TV for good movies that we might all like to watch together. Lately we watched some good old movies and the kids have really enjoyed them. We’ve looked at The Money Pit, Adventures in Babysitting, Calamity Jane, Baby’s Day Out, The Goonies etc.
Cinema – It can be expensive but is a nice way to spend a few hours – there are kids clubs in the mornings in some cinemas and they work out really good value.
Put on a show – we sometimes ask our children to create a show and they take ages rehearsing and practicing and then we get fully entertained.
Hope some of that helps!