I learned a game when I was about 10, and still love it -- it's called "I'm going on a picnic" and it is a mind game that can be played with different ages. The rules: The leader for the round says, "I'm going on a picnic, and I'm going to bring a melon" The next person in the circle, says, "can I bring a melon?" and the leader says yes or no. So the point is to create a pattern. I said "melon" because my name starts with M. The second person can't bring a melon because his name starts with J. But he can bring Juice. and Sam can bring Sand and soda and sofas, and so on. You go around and around, each turn telling the group what you can bring. Then, once everyone figures out what they can and cannot bring, and figure out the pattern, the round ends and another leader comes up with a different pattern. You can get really creative, ie color shirt you are wearing, last letter of the last word that was said, words that have double letters, depending on if the kids can keep up with you. I can tell you that this game lasted 3 hours at a time on sports trips to New England when I was little. For the little one, if she/he wants to play, I would just make an arrangement with the big kids that everything that she says can be brought, so she doesn't get frustrated and the big kids don't get confused.
There is another game that I love that would be great for the older 2. It is orginally a board game, but I don't think you need the board & you can make up some cards in advance. Or take Taboo cards or something like that. So the idea is that you choose 3 totally random word cards, and you have to tell a story with those words in it. But the trick is that the others are listening for weird words, and if they pick the words out of your story, they win points. So, your story has to be wild and convincing, and the words have to placed very carefully so they don't draw attention. But if you get "unicorn" "payday" and "Montana" then you have to be very creative. And put a time limit on it so it doesn't drag on all day.
Also, I love the Fluxx series of games, too, And I would get Apples to Apples Junior. That is a great game, no board needed, just lots of cards, but easy to contain. And they can be used for the storytelling game, too
Ok, enough! Great question, though!