Agreed, there's not too much for them do to (though the BA lounge at Gatwick has a room with Playstations etc). I have taken my son aged 8-9, OK if they are old enough to entertain themselves and can keep quiet, or if they find something they like eg free hot chocolate
They vary so much. It's good to have a quiet area you can go to with free wi-fi, peace and quiet and a bit to eat and drink. Usually have a good selection of free alcohol, but the food you get varies from nuts, crisps and biscuits, to a full spread of cooked and cold foods.
Good if you have a...