Daily Do in Denmark - 06-08

(teaching and memory game) Teachers and students in a Unit 1 training course in Aalborg, Denmark demonstrate "Daily Do", which helps one learn to sing and internalize pitch relationships. The score can be found in the Music Mind Games Handbook and viewed at this page. Watching this video will help to learn this piece. (found on page 29 of the Handbook)

key for daily do

This sounds like it is being sung in G or Ab to me. Is there any reason for the key change? (from C to Ab). Would not the small children would have trouble singing the tonic in this key?