If you're contracting with someone under 18 years of age, the contract would be unenforceable in the court the law (in most jurisdictions). The fix would be to get the custodial parent to sign the contract for the child to do the work. When working with children you would face child labor laws as far as how many hours the kid could work and/or the time of day. If there is a union (acting guild) involved there could be additional restrictions in place that could require you to have a tutor on set for school age kids and more. If kids were to go on tour for music you would have to get clearance from the local state for the artist to perform if past certain hours. The child labor laws will vary from state to state.
"A copyright is a bundle of right that vest with the author of some particular work and it gives them the exclusive right to do a certain thing with that work." It gives the owner the right to make, remake, perform and distribute that work. In music there are two copyrights the first is the copyright of the sound recording or the physical version of the song. The second is the written portion of the song or sheet music will hold a copyright as well.
"In the United States you have to use a mark before it beings to you, you own it through using it." You have to file a federal application to get nationwide priority. The difference between the "R" and "™" is that "R" is the federal registration symbol and you're only entitled to use the "R" after your federal registration issues. The "™" only indicates that you consider that to be your trademark but it really has no legal significance. Just owning a trademark doesn't mean you're going to use it on anything, but as the owner you can license your mark to be used by other. You can find out more by going to www.uspto.gov.
