Sometimes it's difficult to discern the validity of a child's profession of faith. We complicate things further when we look for the wrong thing. When I started out in ministry I remember someone telling me that a child's love for Jesus is a good indicator that he or she is saved. There's some truth to that. Our faith should be evidenced by a change in our affections. We ought to love Jesus and hate our sin. Yet discerning how much a child loves Jesus is difficult to gauge. Indeed, many children grow up "loving Jesus" and admiring him as a great person. So the question of how much a child loves Jesus isn't very helpful. A better question is how much does this child understand (and embrace) the love Jesus has for him. 1 John 4:10 says,
"Herein is love, not that we have loved God but that he loved us and sent His Son to be the propitiation for our sins."
This verse puts the emphasis in the right place. It's not what I do for Jesus that saves me, it's what Jesus has done for me. My salvation (and assurance of salvation) is not based on how much I love Jesus, it's based on how much Jesus has loved me through his substitutionary death on the cross.