Originally Posted by
Productivity
Try to make sure your wife takes your daughter to a different security line to you each time.
This is a good idea - and I concur there is close to a 100% chance you'll have to take it out at LHR.
UK security treats tablets the same way TSA treats computers in the US (apart from Pre-Check line). It's required that they come out and if you don't you are subject to the additional search (as happened to me because I forgot the rule).