Memory work is easier with music. Matthew 6:33, "Seek ye first the Kingdom of God, and his righteousness...." (KJV) is a traditional song.
There are a number of versions available on YouTube, some better than others, some with motions to go with the words to further aid learning by adding a kinesthetic aspect.
Here are a few:
The traditional version:
A more up-tempo arrangement the children might enjoy more:
This one looks like it is using American Sign Language (ASL), but the video is a bit choppy:
Here is another that looks like it is using ASL. The lip-syncing is not perfect on this one. (One choice might be to watch the two ASL versions and learn the signs and teach the song without the video.)