Anyway, I looked it up and I suspect it's probably this ....
Hwyl fawr ffrindiau A goodbye song
Hwyl fawr ffrindiau
Hwyl fawr ffrindiau
Hwyl fawr ffrindiau
Mae’n amser dweud hwyl fawr.
Twr-a-lwr a bant a ni
Bant a ni, bant a ni
Twr-a-lwr a bant a ni
Mae’n amser dweud hwyl fawr.
I found that on the Bookstart site ... there was another song as well ...
Bore da .....A great starter rhyme.
(To the tune of: ‘Frère Jacques’)
Bore da, bore da,
Sut wyt ti?, Sut wyt ti?
Da iawn, diolch.
Da iawn, diolch.
Bore da, bore da.
P’nawn da, p’nawn da,
Sut wyt ti?, Sut wyt ti?
Da iawn, diolch.
Da iawn, diolch.
P’nawn da, p’nawn da.
There was also some bossy-type school stuff...
Good morning! Bore da!
Good afternoon! Prynhawn da!
Come to read Dere / Dewch i ddarllen/ Tyrd I ddarllen
It's story time Mae'n amser stori
Is everyone comfortable? Ydy pawb yn gyfforddus?
Yes we are/No we're not Ydyn / Nac ydyn
Which book is in the bag today? Pa lyfr sydd yn y bag heddiw?
Let's have a look…(plural) Gadewch i ni weld...
The….book is in the bag today. Y llyfr .... sydd yn y bag heddiw
Come to sit down Dere i eistedd/ Tyrd i eistedd (north) Dewch i eistedd
It's song time Mae'n amser canu
Is everyone ready? Ydy pawb yn barod?
That's a good girl! Dyna ferch dda!
That's a good boy! Dyna fachgen da!
What good children! Am blant da!
Well done you! (singular) Da iawn ti!
Well done you! (plural) Da iawn chi!
Wonderful! Gwych!
It's tidy-up time Mae'n amser clirio
Come to help tidy-up. (plural) Dewch i helpu i glirio
Come to help. (plural) Dewch i helpu
It's time to go home Mae'n amser mynd adref
Good bye! Hwyl fawr!
I'll see you next week (plural) Wela' i chi wythnos nesaf
I hope they know all that in Mandarin as well... later on they'll be watching something like this I expect ... Will Cwag Cwac's epic drama " Yr Ig" .....