Looks like the song is in need of a little re-writing:

Mr. Banks:
With tuppence for paper and strings
You can have your own set of wings
With your feet on the ground (nope)
You’re a bird in flight (whether you like it or not)
With your fist holding tight (really tight)
To the string (tail) of your kite

Oh, oh, oh!
Let’s go fly a kite (or the kite flies you)
Up to the highest height!
Let’s go fly a kite and send it (ourselves) soaring
Up through the atmosphere
Up where the air is clear
Oh, let’s go fly a kite! (or the kite flies you)

Bert:
When you send it flyin’ up there
All at once you’re lighter than air
You can dance (flail) on the breeze
Over ‘ouses and trees (and spectators)
With your fist ‘olding tight (death grip)
To the string (tail) of your kite

Londoners:
Oh, oh, oh!
Let’s go fly a kite (or the kite flies you)
Up to the highest height!
Let’s go fly a kite and send it (ourselves) soaring
Up through the atmosphere
Up where the air is clear
Let’s go fly a kite! (or the kite flies you)

Jokes aside – hope that kid was unharmed. Pretty scary.