Hi Natalie,
Campervan holidays on the island of Ireland are becoming really popular as it does indeed combine the accommodation and the ability to travel around all in one!
Wild camping isn't encouraged in Northern Ireland but there are places to camp. If it is possible, then you should gain permission from the landowner. Much of the forest areas of the country are owned by the National Forestry Commission and it is strictly forbidden to wild camp here unless there are clearly designated signs.
That being said, there are campsites that would be available across the
Causeway Coastal Route. Camping Ireland has a wonderful website with the
Ballyness Caravan Park being in an ideal location for the Giant's Causeway and Bushmills. These would be preferable as you have children, there are play areas to keep them amused once you have been out for the day.
There are also some other community posts regarding
wild camping that you may wish to look at.
I hope this helps, and I'm sure your fellow members and industry partners will be able to add to this list!
If you need any more advice, just let me know!
Martin