Does ex opere operato apply to infants? "Ex opere operato" says that a person must have the proper disposition and desire in order to receive graces through sacraments (correct me if I'm over simplifying this). 

Does this not apply to infants when being baptized? 

How do infants receive graces from baptism? 

What is the doctrine regarding infants and "ex opere operato".
I'd say not, but this is just my opinion, and not because I've ever heard of Ex Opere Operato so I'll keep this short and hopefully someone adds a better answer.  But Baptism leaves an indelible mark: 


  Incorporated into Christ by Baptism, the person baptized is configured to Christ. Baptism seals the Christian with the indelible spiritual mark (character) of his belonging to Christ. No sin can erase this mark, even if sin prevents Baptism from bearing the fruits of salvation. Given once for all, Baptism cannot be repeated. 


CCC 1272

Which is more like chiseling yours and your bride's initials into a post with a big heart around it.