Conditional on cryonics being successful, immortality for living, non-frozen people would most likely be successful too, and kids in malaria-infested area, if saved by mosquito nets, would be likely to survive to that day. (And personally I think negligible senescence is more likely to be achieved in the next half century or so than reanimation of cryonic patients to be achieved ever.)

So, unless there's some reason to believe that 1) reanimation of cryonic patients will eventually be achieved, but 2) that won't happen before children living today will be dead, and 3) that cryonic preservation won't get much cheaper in the future than it is today, you are more likely to save a life forever by donating $X to the AMF than $X to this girl on Reddit (even conditional on this not being a scam).