You can use the staffed EU line in this circumstance. If you are EEA and the parent of the children then you really must use the EU line since you and the children may questioned under the child trafficking surveillance that has been ongoing for several years. If you are not the parent then it's not a requirement, but you would be mad not to use the EEA line!

For those looking, if travelling CW you get the fast track UK Border via your boarding pass or frequent flyer card, you don't need a pass as such at T5 arrivals.

If connecting on further to the UK or Ireland, it makes no difference since it's just one area for the Common Travel Area.