We have one of those little fold out couches that we would take with us whenever we went out, less of a pain to cart around than a portacot. If DS got tired we'd just pop that in a friend's spare room or somewhere else quiet and he'd sleep there quite happily until we were ready to go. I could lie down on it too and feed him to sleep which was a bonus. I always take his jaamies and night time nappy too, saves us having to change him when we get home. It's nice to have somewhere for them to sleep, then you can enjoy yourself without having to worry about getting them home to bed.