Here's a trick-taking game variant that works well with three people, that I learned in the Army. I've heard it called a few names, but "Screw the Dealer" seems the most used (adapt the name for use with the kiddos as necessary). It runs like this:
1. The game is played with a standard deck of playing cards, by 3-5 people.
2. There are 19 hands, with the following number of cards dealt to each player in each hand. For a shorter game, or to accommodate little ones with small hands, cut out some of the hands (one could, for example, play a game with rounds of 5, 4, 3, 2, 1, 2, 3, 4, 5; it is recommended to stick with the scheme of decreasing then increasing again, as kids love it).
Hand # 1: 10
Hand # 2: 9
Hand # 3: 8
Hand # 4: 7
Hand # 5: 6
Hand # 6: 5
Hand # 7: 4
Hand # 8: 3
Hand # 9: 2
Hand # 10: 1
Hand # 11: 2
Hand # 12: 3
Hand # 13: 4
Hand # 14: 5
Hand # 15: 6
Hand # 16: 7
Hand # 17: 8
Hand # 18: 9
Hand # 19: 10
3. Dealing the first hand falls to the player who draws the high card in a single dealer-picking draw, after which those cards are returned to the deck. Afterward, each hand is dealt by the person to the left of the person who dealt the last hand. Dealing starts with the person to the left of the dealer for that hand, and goes clockwise.
4. At the end of the dealing, a single card is turned face-up on the deck. The suit of this card is the trump suit for the hand.
4. All game play is clockwise.
5. Each hand starts with a round of bidding, starting with the player to the left of the dealer for that hand. Each person bids a certain number of books they think they will take, in gameplay as described further below. The dealer is not allowed to "lock up" the bidding-- that is, the total number of bids cannot equal the number of cards dealt to each person for that hand. (Thus, for instance, in the 1-card hand, if the first person in a 3-person game bid 1, and the second person bid 0, the dealer would have to bid 1 and hope for the best.) The scorekeeper records each person's bid.
6. Gameplay then proceeds as a series of throws, until all the cards dealt are exhausted. In each throw, the person beginning throws down a single card face up, then each person throws down a single card face up, proceeding clockwise until all have thrown a card. The first throw begins with the person to the left of the dealer; each subsequent throw begins with the person who won the last book, as described further below.
7. If the trump suit has not yet been played, the person beginning the throw cannot begin it by playing a trump card. Aside from that restriction, the beginning person can play any card from her hand.
8. Each subsequent person must play a card in the led suit, if he has one. Otherwise, he can "throw off" any suit he desires.
9. At the end of all the throwing around the circle, the person who played the highest card in the led suit wins that throw, UNLESS the led card was not a trump, and one or more trumps were played, in which case the highest trump card wins that throw. The completed set of cards thrown by the players for that throw is called a "book", and the player winning the book takes the cards from the middle, turns them upside down, and neatly stacks them in front of her.
10. At the end of the hand, when all cards have been played and all books taken, scoring for each player is recorded for the round. Each book taken entitles the taker to 1 point, and each player who gets the exact number of books bid by that player gets a bonus of 10 points. (Variants can be played with a number of different bidding and sandbagging rules, as will be familiar to players of these sorts of trick-taking games.)
11. The score for each round is added to the running total for the player. The player with the highest score at the end wins the game.
It is a pretty fun game that can be completed in a predictable amount of time, shortened by reducing the number of hands. DS5 loves it. It teaches a lot of skills, with a lot of fun introduced by the need to adjust bidding based on the number of cards and the "screwing the dealer" factor.
What I did for DS5, to help him work on his penmanship, is create a scoresheet for this game. I'll post a link to it later from home. I would enjoy hearing if anyone tries and likes the game.
ETA: It looks like it is very similar to a whist variant most often called "Oh, Hell", with maybe some minor differences:
http://en.wikipedia.org/wiki/Oh_Hell