Here are two little pieces that I use in first lessons (both are Noteflight scores):
Trot Old Joe uses only the B, G and D strings and Bells adds the A on the third string. Students are pleased to be able to play a little song and these few notes are easy to remember. I’ve used these with students as young as 3 and as old as 9 or 10. Some never forget them and play them as fun pieces for years!
Michael