Hi Alison,
It's so lovely you'll be over this spring with your whole family for a wedding in Dundalk! It's a great idea to take this opportunity to spend some time exploring the north-west coast too. :)
Donegal and
Sligo have some wonderful sights to see, and I definitely recommend
County Mayo as well. Is there anything in particular you wouldn't want to miss? Depending on where you'd like to go, you can look into the perfect place for your family to stay. Are you thinking of staying in one place and using it as a base to explore the area, or would you like to move from location to location and stay in different accommodations along the way?
You can find some recommended self-catering suggestions for Donegal
here, and for Sligo
here. Most will be suitable for children of all ages, but it's always handy to reach out beforehand for more information.
Also, have you thought about how you'd like to travel from the east coast to the west coast? There is a great
trip idea here that takes you along all of the hidden gems between Dublin and Galway. :)