The plan that's even better won't be about "rescuing the child" in particular, and for the same reason you can't issue specific wishes to FAI, like to revive the cryopreserved.
But whatever the "better plan" might be, we know the FAI won't leave the child there to die a horrible death. To borrow Eliezer's analogy, I don't know which moves Kasparov will make, but I do know he will win.
This is our monthly thread for collecting arbitrarily contrived scenarios in which somebody gets tortured for 3^^^^^3 years, or an infinite number of people experience an infinite amount of sorrow, or a baby gets eaten by a shark, etc. and which might be handy to link to in one of our discussions. As everyone knows, this is the most rational and non-obnoxious way to think about incentives and disincentives.