Have you tried Sequence? It's fun and very simple to learn - a combination of a board and a card game. The concept is basic - make a row of five chips on the board, based on what cards you have in your hand, but you can learn strategy that makes it fun for all ages.
We used to play scattegories without the actual game bought from the store. We would think of ten categories, (ie. body of water, plants, foods, colours, famous people, etc.) then pick a letter, and set a time limit. Everyone had to write down something for each category starting with that letter before the time was up. Then we all read off our words, one category at a time. If any one else had the same word, we lost a point. Each word started with a 10 point value. (So if I wrote down alligator, but my mum and sister did too, it was worth 8 points for each of us.)
And, have you tried speed scrabble? You play without a board, and each person makes their own set-up of words in front of them. You start with 7 letters, and as soon as one person has their seven letters made into words (that connect as they must on a scrabble board) he/she says "pick four" and everyone must pick up four new letters to add to the words in front of them. Again, when one person has used all their letters, everyone must pick up four new ones. The idea is not to get left behind with a pile of unused letters! When there are no letters left to pick up on the table, the first person to use up everything in their hand says "stop", and everyone must stop, and count any letters left in their hand as points against them. (according to the point value on the piece.) Then you count up all the points in the words you made in front of you, and total your score. It's simpler than scrabble, and you don't have to think of long words at all, or worry about placing them strategically on the board, so it's easier for kids. We have a lot of fun with it.
Hope you find something good!