The 'Peter Pan Alphabet' doesn't actually say that Peter pulled a lion's tail, although it could be implied from the verse:
'L is the Lion who lashed his Fierce Tail,
And did Peter Tremble? did Peter turn Pale?
Not much! 'Twas the Lion who moved to adjourn,
He couldn't turn Tail, Peter Left none to Turn'.
As for references of Peter confronting a lion, the novel mentions lions living in Neverland and Peter's 'defiance of the lions' (chapters 5 and 7) but as far as I could see, not in the play (I might have missed it...). Since the novel was published in 1911, 4 years after Herford's Alphabet, it's unlikely anyway that the latter got its inspiration from the former.
Having said that, the Alphabet has some very strange examples for the letters, some of them having no relevance to the story - G for Old Glory? The White House? X-Ray? So, a lot of nonsense and whimsy all round!