The batting order for a 8U rec league team should be set so that each kid gets the same number of at bats throughout the season, assuming all kids are making all the games. That means sometimes batting your weakest batters at the top of the lineup.
I started coaching rec at the 10u level since we do not have 8u here. We did however have 7 and 8 year olds on our 10u team. I tried to be "tricky" during my first season. Started the season by trying to model my lineup after pro-lineups; Speed at top, then power, etc. After a couple of weeks I switched to a structure similar to that shown on the link marriard posted. Unfortunately, it didn't work for us. By having the "weaker" batters scattered throughout the lineup, it always seemed as though we would have the bases loaded with 2 outs when one of those hitters came up - inning over... Our "left on base" numbers were huge. I kept playing around with it and never found a structure I liked.
Entering my second season (still at 10u but with more 8 and 9 year olds at that point), I switched to a structure similar to what Lobster Birch is suggesting. Prior to game 1 I created what I thought would be the best possible lineup with our players. I then kept track of who batted last in each game. The person on deck became my lead off hitter for the next game and I simply continued on with the same exact lineup. So basically a perpetual batting order that lasted 16 games. If I ever get back into the younger levels of rec ball, that is what I will go back to.