Sadly, except in imminent danger of death, you cannot do that. You have no authority to make that decision on behalf of the child, I know, that sounds wrong, but so far as I am aware, surreptitious baptism of infants whose parents do not want to have them baptized, is simply not allowed. If there is any traditional defense of doing so, again, outside of danger of death, I am unaware of it and will stand corrected.
I know it is liberal Red Sea propaganda, but this actually happened (albeit in an Episcopal church) in an episode of All In The Family where Archie feared for the soul of his grandson Joey. Again, AITF was propaganda, but some of its scenes were done incredibly well, and the show did have its good points. This is one of them.
That was probably an invalid baptism (just rubbing Joey's forehead with a wet finger), but granting poetic license, God bless him, Archie at least said "Holy Ghost". Well done.