At young ages, we strongly recommend not having too many set plays. Most coaches find that they are more successful when they can run a few plays really well than a lot of plays poorly. One approach is to start the year with a good play against a man D, and a good play against a zone, then focus practice on the fundamentals that will help them to execute the plays successfully. As the season progresses and the players get proficient you can slowly add new plays, or even better, variants of the existing plays.
It takes a long time to teach a group of 4th graders a complicated play, and during a game, it only takes one kid forgetting where to go to ruin it. When plays are too complicated or there are too many, kids often focus only on trying to be in the right spot and do not develop the basketball fundamentals and decision making needed to excel and feel comfortable in a game. And if you change your mind and try a new play, you are starting all over.
Remember, good skills will translate into any plays.