A la puerta del cielo is in the DT but I found another verse in Cantos populares españoles (T.1) by Francisco Rodríguez Marín. So here are the 3 verses with the accents:

A LA PUERTA DEL CIELO

1. A la puerta del cielo venden zapatos
Para los angelitos que andan descalzos.

Estribillo: Duérmete, niño, duérmete, niño
Duérmete, niño, arrú, arrú.

2. A los niños que duermen Dios los bendice,
A las madres que velan Dios las asiste.

3. A tôs los niños güenos Dios los bendice
Y a los que son malos les da lombrices.

Translation (non singable!):

1. At the gate of Heaven they sell shoes
For the little angels who go barefoot.

Chorus: Sleep baby, sleep baby,
Sleep baby, lullaby, lullaby.

2. God blesses the babies who sleep,
God helps the mothers who watch [over them]

3. God blesses all the good babies,
To the ones who're naughty He gives earthworms.

Notes:
-The babies are also called "angelitos".
-Arrú, arrurú, arró, arroró are the words that mothers chant to their babies to lull them to sleep. The verb is "arrullar".
-"tôs" is short for "todos" as the "d" between vowels is dropped and the two o's are merged.
-"güenos" is "buenos" -you don't want a linguistics class, do you?

I like the eartworms thing! We have it on Mama Lisa's Word on Mexico page and Spain page but Lisa hasn't posted the 3rd verse yet. (Self advertizing!)