Tennis court for Kids' Training.

My children are very interested in tennis these days. They watch almost every tennis match on TV. They made me buy almost every tennis video games out there, along racquets, balls and shoes. So why not let them get good at the game. So, I am planning to build a tennis court in my backyard. They are just 10 and 12 years old. We have a tennis court designer team nearby, who builds standard sized tennis court on the backyards. But I am confused. Should I go for a standard size court or is there a court size that suits for children's training purpose. I am worried if they are not able to play well in standard size court, they will get depressed. Any suggestions about it?