I was raised on the philosophy that before “the age of accountability” children that died went to heaven. I don’t believe that’s necessarily true any more. Actually I don’t know what I believe. I haven’t done enough research, but I’ve read enough to know that long held belief may not be rooted in Scripture.
Here are the links Jeff posted to the MacArthur works. Just skimming them right now, they look very good. Both use Luke 18:15-17 as text.