to push or not to push

How do you decide what to let your kids (or grandkids) do? Or should you push them to do things. Gymnastics, dance, soccer, volleyball, swim ... and on and on and on. You want them to be well rounded but not so busy with activities that they have no time for friends, family and relaxation. I am a huge soccer freak. I want Jamie to play soccer. She did a summer mini kicker class but sometimes she seemed to like it and other times not. should you make them try everything or how do you choose? i love to watch soccer, tennis and basketball, is that what I send her to? she loves music, do i let her play the piano or wait until they offer it in school? I do not want her to be one of those kids who does a couple of things but only does them half way. I want her to be a happy healthy kid who enjoys herself whatever she does.