Well, I haven't heard from David yet, but I was with some other local musical know-it-alls last night, and here's what I learned:

The song shows up in the wonderful collection by Sol Weber, "Rounds Galore " attributed to "William Shield, folk-processed"

The words as printed are:

We wish you a happy birthday,
A joyous and celebrated birthday.
For you, dear (insert name),
We wish you a long, long life.

I've emailed Sol to ask what he knows. If I don't hear from him soon, I'll be seeing him at Pinewoods camp in a couple of weeks and will ask him then!

Allison