@daniel specificially asked for a “kid friendly” hymn for the Transfiguration gospel. IMO the Laurence Housman text referred to by @canadash has a couple of scansion problems in the first two lines; it’s not terribly “Transfiguration-ish,” (The Hymnal 1982 even assigns the hymn to its “Epiphany” section along with several other Baptism of the Lord texts); and the final stanza has a theological problem if the line “To you, the King of glory, now” is heard without the second comma.

I think J. Armitage Robinson’s “’Tis Good, Lord, to Be Here,” sung to SWABIA, would be much more “kid friendly.” The text, as updated in the 1996 Voices United: The Hymn and Worship Book and subsequently appearing in several hymnals, including Gather 3rd edition, Worship 4th edition and Oramos Cantando: We Pray in Song, is:

1 How good, Lord, to be here!
Your glory fills the night;
Your face and garments, like the sun,
Shine with unborrowed light.

2 How good, Lord, to be here,
Your beauty to behold
Where Moses and Elijah stand,
Your messengers of old.

3 Fulfiller of the past
And hope of things to be,
We hail your body glorified,
And our redemption see!

4 Before we taste of death,
We see your kingdom come;
We long to hold the vision bright
And make this hill our home.

5 How good, Lord, to be here!
Yet we may not remain;
But since you bid us leave the mount,
Come with us to the plain.

Both the text and tune (SWABIA) are in the public domain.