When my kids were teenagers I was at uni and had no money. I bought a family railcard and went out and about very cheaply - I could take 2 adults and 4 children, the adult was reduced fare and kids something like £1 or 2. We even went camping in St Ives, just me and my kids and their friends, all the rucksacks, tents, equipment and all - on the train. It was great! OH stayed at home (sitting out of that one, he said) and did some decorating but they were memories I wouldn't trade for the world (even when I woke up one morning and my tent was like a water bed!) x