If you are interested, Dave Hunt wrote an excellent book that can give you a better understanding of what John Calvin was all about: What Love is This?
I have learned this past couple of years that Calvinists who are consistent (like James White mentioned by Eric upthread) honestly do not believe that infants and children head strait to Jesus if they die, talk about unthinkable
But that's something dating back to Augustine and the early days of Roman Catholicism. They taught that if an infant didn't get baptized it was going strait to hell. An example given was two mothers had newborns. One mom was a known prostitute and the other a God loving, church attending mom. As each journeyed to get their infant baptized the godly mother was involved in an accident that killed her baby. The prostitute's infant was baptized.
Augustine and the RCC taught that the godly mom's baby went to hell.