I think your and LondonAndy's point on this is crucial, I think that anyone going there with a guest + young child claiming entry as an entitlement would be very likely to be rebuked (and very legitimately so in my view should I add). When you ask it as a favour, my guess is that things go back to sunrisegirl's earlier point. If you are there at a pretty empty time, the lounge is fairly quiet, etc, lounge attendants may well let you in; but if the lounge is very busy, lounge attendants know that it is a period of school holidays with lots of families with young children asking the same privilege they would in my guess be more likely to say no. As long as someone is happy to gracefully accept the answer whether it is a 'yes' or a 'no', i'm personally not shocked by them asking.