There are probably a few mistakes here. I'm not very good with identifying songs, 
so please correct me if you find a mistake!! As far as the strumming, its pretty 
much just like quarter notes. Listen to it on youtube... Some other parts are 
single strum, where I pointed it out. :)

Thanks! Enjoy...

Key of E, no capo

OOOOOOOOOOH!
E
Happy Hogwarts Birthday!
F#m
Magic wizard birthday! Fun wizard
                 E
happy birthday! Fun fun fun fun!

Magic flavor birthday cake!
A
Wizard wishes you will make!
F#m
Happy birthday dance with everyone

2, 3, 4...

C#m (single strum until chorus)
Birthday magic wand!
E
Party happy birthday!
C#m
Wizard party school!
F#m
Magic magic wizard magic party!
C#m
Gryffindor! Party more!
E
Hufflepuff! Wizard stuff!
C#m
Ravenclaw! Hell naw!
F#m
Pretty sure that's everybody!

E (strum again)
Happy Hogwarts birthday
F#m
Wizard School party! Children eating cake inside their
E
mouths!
D#
Hogwarts lesson number 1
A
Never not be having fun!
B                       A
Children eating cake inside their
E
mouths!