Anyone and anything can “negotiate”, if one party wants to submit the terms to a magic 8-ball for approval, that’s their right, a minor, even a newborn, would be no different.
But there’s nothing forcing the other party to participate other than their own desires, if they view the other party submitting the terms to a magic 8-ball or to the cry of a newborn as unreasonable, they can walk away.
In this case it seems like the contract is actually about and for the minor, so the other side is unlikely to consider it unreasonable to negotiate with the minor.
Still, as with having a lawyer or some other more traditional representative doing the negotiations, it’s not binding until the parties actually agree to the terms.