So somepony on the Skype chat said you needed singers. As luck would have it, I'm a singer and a Beatle Brony (Peanut Crunch). I'm primarily a writer for the group, but my main area of study is singing.
If I could make a couple recommendations (as a fellow rewriter of popular songs).
1. Maybe use "dear miss Pinkie Pie" instead of "Mrs. Pinkie Pie." Miss is a bit more contextually flexible, and the words also fit the same syllable scheme.
2. Is the (hey hey hey) temporary? Smi-hi-hi-hi-hi-hi-hile would be one way to go.
3. "you and your smiles" feels a bit repetitive. I won't try and tell you what to fill that spot with, but it's an observation. You could also rewrite the third line which also talks about smiles.
Again, these are just recommendations and you can take or leave them.
until