Though you have not seen him, you love him. Though you do not now see him, you believe in him and rejoice with joy that is inexpressible and filled with glory, obtaining the outcome of your faith, the salvation of your souls.(1 Peter 1:8-9 ESV)
This should be my prayer every day for my kids; to know the joy of their salvation — the grace, forgiveness and sanctification of God in Jesus Christ. May they grow in understanding of the riches of the gift they have received in Christ and as their knowledge increases that their joy will deepen.
I like these verses from 1st Peter because the emphasis is on loving God, rejoicing in Him as the One in whom we are saved. With belief like this a child can endure much and remain steadfast in Christ. When our trust is in who Jesus is and our joy is in knowing Him there will always be cause to rejoice even in the worst of times.
Nothing is more important than praying for our children to know Jesus in this way, for them to obtain joy inexpressible and the salvation of their souls.