So for ukulele it's just regular tablature, I've researched and tried a few other variations with kids but didn't find anything that's easier. The songs are mostly the same as for piano, and a few of them is also written in the same key so you can play along with each other.
T is Tablature and LC is Lyrics & Chords,
then later on I will also add guitar-like soundfiles (S). Just click the icons and the papers pop up in a new window ready to be printed. If you don't have a program to open .pdf files with, you can click here for a safe AR download.
Song
T
LC
S
Ba, Ba, Vita Lamm
Bjornen Sover
Bjallerklang (Jingle Bells)
Blinka Lilla Stjarna (Twinkle, Twinkle, Little Star)