For the Gaiety panto last year, we has seats at the front of the balcony. The 7yo & 5yo had a great uninterrupted view. We've booked seats in the same row for this year.
If you can get a box on the dress circle, so much the better - you can move the chairs around to suit yourselves, and the view is excellent (particularly from the ones furthest away from the stage).
Just be sure they can see over the barrier at the front of the balcony, I'm not sure if the Gaeity do booster cushions for small children, might be worth a call to check and bring your own if they don't.