A person cannot be coerced into agreeing to a contract, where having a gun put to your head is clearly coercion and being told "we won't give you a free toaster if you don't sign" is not coercion. A child can sign a contract, but that contract may not be enforceable, depending on whether the child is a minor (e.g. under 18). If we are speaking of a minor and given the question (it's not an educational loan agreement etc), the contract with FB cannot be enforced by FB without you reaffirming the agreement.
When you agree to the TOS, you acquire certain contingent rights to "stuff", as does FB. Their main enforcement hammer is that they can disable or delete your account. They have sole discretion to determine whether you have violated their rules. If they cancel you, you could attempt to sue them in court for breach of contract, which would require you to affirm the contract, then you would face the challenge that they have sole discretion to determine whether you have violated the rules, which is a really low bar for them to clear. If you disaffirm the contract, it is game over for you anyhow, since your loss of "rights" follows from the fact that you were not legally competent to enter into the contract.
An alternative is that you don't cancel the account but you want to sue then for distributing your stuff, where you allege that they do not have a valid contract allowing them to distribute your stuff. This is the case in CMD v. Facebook, where the court held that the agreement was valid because plaintiffs had not in fact disaffirmed the contracts (under California law).
Separately, you can be sued for copyright infringement or even prosecuted for unauthorized computer access. If your account has been deleted, it would be a crime to hack into FB to overcome the loss of access rights. Presumably you would not do any such thing.
One of the rights that FB gains under the TOS is a revocable license to distribute the intellectual property that you upload. Suppose that you don't want to allow them to ever distribute your IP, then you can refrain from uploading any content. Uploading content can be taken to be a reaffirmation of the agreement (although you can change your mind and delete the content whereupon the license is revoked, per the TOS). But bear in mind that when you upload content, you may also also be giving permission to others to use – e.g. copy – that content, and the TOS does not have a clawback clause compelling other users to know whether you have deleted said content and delete content of yours that you have deleted.
In other words, it could be a contract, but you could disaffirm the contract at least up to age 18.