It's great that you are visiting Northern Ireland with your kids soon!
There are many places they might enjoy in Belfast and surroundings. I can for instance recommend you a family walk to Cave Hill or a trip to the Giant's Causeway
. In the city, Belfast Zoo
and Titanic Belfast
are also kids friendly things to do. And the Vertigo inflatable park
in the Titanic Quarter might also be really fun for them.
You'll find many more kids activities suggestions on the Family Fun website
I hope this helps! What else have you got planned during the rest of your stay?