If they're tired, sick, tender or just bored, a book is ALWAYS the solution. You could read to my girls for an hour and they would ask for more. Even though all three can get through books on their own now (albeit beginning readers for the twins) they all prefer to be read to. However, when I am tied up and my kids are needy, I always redirect them to books. It spells relief for all.
A favorite outing is to our local library. We have between 20 and 40 books out at all times. It makes me smile when I return them, knowing we read each one at least once.
Here Adeline stumbled over my bag of library books when walking through the door. That was it for her. She sat right down and looked though each one.