How can I apply for an EB-5 visa while in the United States on a visitor visa?

While you can technically apply while in visitor visa status, they cannot attend school until after the adjustment receipt is issued. Also, if they enter with an intent to adjust, that is visa fraud. If you did not enter with an intent to adjust and just now learned you can, then you can apply, but advising your family to enter to adjust is not something a lawyer can do.

If you are applying for EB-5 and eligible to file a concurrent I-485, your spouse and minor kids can file I-485 as dependents when in the US and kids can attend school. Keep in mind nonimmigrant visa misrepresentation issue when filing to immigrate and discuss this with an experienced immigration lawyer prior to filing.

The kids cannot go to school on a visitor visa, but they can once their I-485s have been filed.

If you are eligible to file an I-485 and if your spouse and child are legally admitted and if they file I-485s, then yes, your child can attend school in the U.S. without violating her status.